I can't add user to Participant Administration.

You are going to need to add some more details. 

method server log file at the time of performing this operation is a good start.

Hi ​@ptc-6532716,

Could you please clarify what you mean by can't add a user to Participant Administration?

whether your goal is to create a new user or search for an existing user?
Could you please provide a screenshot of the issue?
Are you seeing any error messages in the UI? If so, please share a screenshot of the error.