strange behavior of pgbouncer

Hi,

I am using pgbouncer 1.16 that is installed on host A and users are
connecting through pgbouncer on host A to connect to the postgres database
that is installed on host B. Postgres db version is 12 and both hosts are
running on Centos 7 OS.

I have 2 users in userlist.txt file user1 and user2. Both users have the
same passwords.

Through Pgbouncer, if I connect through user1 I get an error message of
"password authentication failed", but I don't get this error while I
connect through user2, although the "passwords are the same" and Previously
both users were working fine.

I don't know what happened that caused that error.

I checked pgbouncer and db logs both but both log files have the same issue
i.e. password authentication failed for user1 while I try to connect
through pgbouncer using user1.

and when I use the same password to connect to the *db directly* by both
users user1 and user2 , I don't get any error.

Could you help me with this? How can I troubleshoot this? Is there any way
to block any particular user from connecting through pgbouncer? How to
check this ?