HyperDB connection problem

There was a problem connecting to the databases. Here's the wpdb object:

hyperdb Object
(
    [last_table] => wp_options
    [last_found_rows_result] => 
    [save_queries] => 
    [dbh] => 
    [dbhs] => Array
        (
            [global__r] => 
        )

    [hyper_servers] => Array
        (
            [global] => Array
                (
                    [read] => Array
                        (
                            [1] => Array
                                (
                                    [0] => Array
                                        (
                                            [host] => el1-prod-cluster.cluster-cenqehearbvh.us-west-2.rds.amazonaws.com
                                            [user] => el1
                                            [password] => m0nk3ysl4b
                                            [name] => ebdb
                                        )

                                    [1] => Array
                                        (
                                            [host] => el1-prod-cluster.cluster-ro-cenqehearbvh.us-west-2.rds.amazonaws.com
                                            [user] => el1
                                            [password] => m0nk3ysl4b
                                            [name] => ebdb
                                            [write] => 0
                                            [read] => 1
                                            [timeout] => 0.5
                                        )

                                )

                        )

                    [write] => Array
                        (
                            [1] => Array
                                (
                                    [0] => Array
                                        (
                                            [host] => el1-prod-cluster.cluster-cenqehearbvh.us-west-2.rds.amazonaws.com
                                            [user] => el1
                                            [password] => m0nk3ysl4b
                                            [name] => ebdb
                                        )

                                )

                        )

                )

        )

    [hyper_tables] => Array
        (
        )

    [hyper_callbacks] => Array
        (
            [db_connection_error] => Array
                (
                    [0] => wpdb_connection_error
                )

        )

    [save_query_callback] => 
    [persistent] => 
    [max_connections] => 10
    [check_tcp_responsiveness] => 1
    [min_tries] => 3
    [srtm] => Array
        (
        )

    [db_connections] => Array
        (
            [0] => Array
                (
                    [dbhname] => global__r
                    [host] => el1-prod-cluster.cluster-cenqehearbvh.us-west-2.rds.amazonaws.com
                    [port] => 3306
                    [user] => el1
                    [name] => ebdb
                    [elapsed] => 0.10254502296448
                    [success] => 
                )

            [1] => Array
                (
                    [dbhname] => global__r
                    [host] => el1-prod-cluster.cluster-ro-cenqehearbvh.us-west-2.rds.amazonaws.com
                    [port] => 3306
                    [user] => el1
                    [name] => ebdb
                    [elapsed] => 0.011411905288696
                    [success] => 
                )

            [2] => Array
                (
                    [dbhname] => global__r
                    [host] => el1-prod-cluster.cluster-ro-cenqehearbvh.us-west-2.rds.amazonaws.com
                    [port] => 3306
                    [user] => el1
                    [name] => ebdb
                    [elapsed] => 0.02120304107666
                    [success] => 
                )

            [3] => Array
                (
                    [dbhname] => global__r
                    [host] => el1-prod-cluster.cluster-cenqehearbvh.us-west-2.rds.amazonaws.com
                    [port] => 3306
                    [user] => el1
                    [name] => ebdb
                    [elapsed] => 0.0091509819030762
                    [success] => 
                )

        )

    [open_connections] => Array
        (
        )

    [last_used_server] => 
    [used_servers] => Array
        (
        )

    [save_backtrace] => 1
    [default_lag_threshold] => 
    [dbh2host] => Array
        (
        )

    [dbhname_heartbeats] => Array
        (
        )

    [is_mysql] => 1
    [show_errors] => 
    [suppress_errors] => 1
    [last_error] => 
    [num_queries] => 0
    [num_rows] => 0
    [rows_affected] => 0
    [insert_id] => 0
    [last_query] => SELECT option_name, option_value FROM wp_options WHERE autoload = 'yes'
    [last_result] => Array
        (
        )

    [result:protected] => 
    [col_meta:protected] => Array
        (
        )

    [table_charset:protected] => Array
        (
        )

    [check_current_query:protected] => 
    [checking_collation:wpdb:private] => 
    [col_info:protected] => 
    [queries] => 
    [reconnect_retries:protected] => 5
    [prefix] => wp_
    [base_prefix] => wp_
    [ready] => 
    [blogid] => 0
    [siteid] => 0
    [tables] => Array
        (
            [0] => posts
            [1] => comments
            [2] => links
            [3] => options
            [4] => postmeta
            [5] => terms
            [6] => term_taxonomy
            [7] => term_relationships
            [8] => termmeta
            [9] => commentmeta
        )

    [old_tables] => Array
        (
            [0] => categories
            [1] => post2cat
            [2] => link2cat
        )

    [global_tables] => Array
        (
            [0] => users
            [1] => usermeta
        )

    [ms_global_tables] => Array
        (
            [0] => blogs
            [1] => signups
            [2] => site
            [3] => sitemeta
            [4] => sitecategories
            [5] => registration_log
            [6] => blog_versions
        )

    [comments] => wp_comments
    [commentmeta] => wp_commentmeta
    [links] => wp_links
    [options] => wp_options
    [postmeta] => wp_postmeta
    [posts] => wp_posts
    [terms] => wp_terms
    [term_relationships] => wp_term_relationships
    [term_taxonomy] => wp_term_taxonomy
    [termmeta] => wp_termmeta
    [usermeta] => wp_usermeta
    [users] => wp_users
    [blogs] => 
    [blog_versions] => 
    [registration_log] => 
    [signups] => 
    [site] => 
    [sitecategories] => 
    [sitemeta] => 
    [field_types] => Array
        (
            [post_author] => %d
            [post_parent] => %d
            [menu_order] => %d
            [term_id] => %d
            [term_group] => %d
            [term_taxonomy_id] => %d
            [parent] => %d
            [count] => %d
            [object_id] => %d
            [term_order] => %d
            [ID] => %d
            [comment_ID] => %d
            [comment_post_ID] => %d
            [comment_parent] => %d
            [user_id] => %d
            [link_id] => %d
            [link_owner] => %d
            [link_rating] => %d
            [option_id] => %d
            [blog_id] => %d
            [meta_id] => %d
            [post_id] => %d
            [user_status] => %d
            [umeta_id] => %d
            [comment_karma] => %d
            [comment_count] => %d
            [active] => %d
            [cat_id] => %d
            [deleted] => %d
            [lang_id] => %d
            [mature] => %d
            [public] => %d
            [site_id] => %d
            [spam] => %d
        )

    [charset] => 
    [collate] => 
    [dbuser:protected] => 
    [dbpassword:protected] => 
    [dbname:protected] => 
    [dbhost:protected] => 
    [func_call] => $db->query("SELECT option_name, option_value FROM wp_options WHERE autoload = 'yes'")
    [incompatible_modes:protected] => Array
        (
            [0] => NO_ZERO_DATE
            [1] => ONLY_FULL_GROUP_BY
            [2] => STRICT_TRANS_TABLES
            [3] => STRICT_ALL_TABLES
            [4] => TRADITIONAL
        )

    [use_mysqli:wpdb:private] => 1
    [has_connected:wpdb:private] => 
    [categories] => wp_categories
    [post2cat] => wp_post2cat
    [link2cat] => wp_link2cat
    [table] => wp_options
    [callback_result] => 
    [dataset] => global
    [dbhname] => global__r
    [lag_cache_key] => el1-prod-cluster.cluster-cenqehearbvh.us-west-2.rds.amazonaws.com:3306
    [lag_threshold] => 
    [time_start] => 1511567414.8843
    [last_connection] => Array
        (
            [dbhname] => global__r
            [host] => el1-prod-cluster.cluster-cenqehearbvh.us-west-2.rds.amazonaws.com
            [port] => 3306
            [user] => el1
            [name] => ebdb
            [elapsed] => 0.0091509819030762
            [success] => 
        )

)

Here is the SERVER (ENV) variable for DB_REPLICAS:

el1-prod-cluster.cluster-ro-cenqehearbvh.us-west-2.rds.amazonaws.com

And here is the DB_REPLICAS constant:

a:1:{s:8:"replica1";a:8:{s:4:"host";s:68:"el1-prod-cluster.cluster-ro-cenqehearbvh.us-west-2.rds.amazonaws.com";s:4:"user";s:3:"el1";s:8:"password";s:10:"m0nk3ysl4b";s:4:"name";s:4:"ebdb";s:5:"write";i:0;s:4:"read";i:1;s:7:"dataset";s:6:"global";s:7:"timeout";d:0.5;}}