The one thing that can cause this suddenly is password expiration in PostgreSQL, though this is not typical. Most likely the password changed on one of the sides, so check that first.
PostgreSQL allows you to specify that a password expires at a specific timestamp. So you can:
ALTER USER foo WITH PASSWORD 'bar' VALID UNTIL 'tomorrow';
And foo will be able to log in with the password 'bar' until the next day at system time....
So if you can verify that the password did not change on both sides, try this:
ALTER USER foo WITH VALID UNTIL 'infinity';
Of course substitute your real user for foo
. This will clear any expiration, or rather move the expiration time indefinitely into the future.