We are facing an issue with one user where the password is static, but keeps on changing by ppmuser, kindly advice.
TPAM is very dumb. It only does what it is told so this is most likely a configuration issue.
A little more information is needed here to make a suggestion that will not be a compete guess.
You talk about a user. Users authenticate to TPAM to do "Stuff". TPAM does not usually manage "Users" passwords.
So is it a TPAM "managed account" that is associated with a "System" you are having an issue with?
If so then details of the system it is on, if there are other accounts associated with this system, has it ever worked, is it a newly configured account etc will help to try to provide assistance.