We had a NagVis and CAPC integration failure due to the user's password expiring. Could you please consider the possibility that the user does not have a password expiration date in CAPC
External user's passwords should not be affected by the password lifespan.
this is a know defect and is fixed in 3.7.5 and newer versions.
Release : 19.1
Component : IM Reporting / Admin / Configuration
update user_definitions set PasswordExpiration=0 where name='username';
select PasswordExpiration from user_definitions where username = <username>;