Postgres 13 streaming replication standby not sending password, 'fe_sendauth: no password supplied'

Hello,

I'm building a new 2-node Postgreql 13 streaming replication cluster. I'm able to clone the primary to the standby using pg_basebackup.
However, the standby is unable to authenticate to the primary to begin recovery during startup. It logs an error, "FATAL: could not connect to the primary server: fe_sendauth: no password supplied".

I've tried using both .pgpass and passing the password explicitly in the myrecovery.conf primary_conninfo string. Debug logs on the primary show the initial connection. but no user provided and no authentication attempt.

pg_hba.conf on the primary:
host all,replication repl primary-database-server scram-sha-256
host all,replication repl standby-database-server scram-sha-256

myrecovery.conf on the standby:
primary_conninfo = 'host=primary-database-server port=5432 user=repl application_name=standby-server-name'
recovery_target_timeline = 'latest'
primary_slot_name = 'standby_replication_slot'

.pgpass on the standby:
# hostname:port:database:username:password
*:*:replication:repl:repl_user_password

I've triple-checked that the password in .pgpass matches the password set for the repl user in the database, and the repl user has REPLICATION access.
I'm able to connect to the primary server using the repl user and the psql client, both via .pgpass and providing the password directly.
I can't figure out why the standby postgres server is skipping the provided credentials when connecting to the primary.

Thank you for your time,

Will Keaney

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