Error while setting up pgactive extension

I am following the AWS's documentation to setup pgactive extension and have an active-active setup on two AWS RDS Postgres instances. Following all the steps successfully till step 11 where it asks to run the following on endpoint-2:

SELECT pgactive.pgactive_join_group(
    node_name := 'endpoint2-app',
    node_dsn := 'user_mapping=postgres pgactive_foreign_server=pgactive_server_endpoint2',
    join_using_dsn := 'user_mapping=postgres pgactive_foreign_server=pgactive_server_endpoint1'
);

Getting the following error:

ERROR:  could not connect to the server in replication mode: connection failed
CONTEXT:  SQL statement "SELECT *                           FROM _pgactive_get_node_info_private(node_dsn)"
PL/pgSQL function _pgactive_begin_join_private(text,text,text,text,boolean,boolean,boolean) line 66 at SQL statement
SQL statement "SELECT pgactive._pgactive_begin_join_private(
        caller := '',
        node_name := node_name,
        node_dsn := node_dsn,
        remote_dsn := join_using_dsn,
        bypass_collation_check := bypass_collation_check,
        bypass_node_identifier_creation := bypass_node_identifier_creation,
        bypass_user_tables_check := bypass_user_tables_check)"
PL/pgSQL function pgactive_join_group(text,text,text,integer,text[],boolean,boolean,boolean) line 43 at PERFORM

The postgres users on both RDS1 and RDS2 are a member of rds_superuser and rds_replication role. Both the RDS Instances are associated with the same Security Group. I ran dblink_connect to check the connectivity b/w both the RDS instances and it gives an OK result. So, I am not sure what else to check here? Can someone recommend how to take care of this issue?

RDS Instance - t3.medium Postgres version - 16.3