Add Reviewer Showing Error (Ojs-3.3.0-21)

[scholarsync.projects]

In my ojs 3.3.0-21 version journal (ijraps.in), which I updated from version 3.2.0 to 3.3.0-21 and its working fully fine but whenever I get into assigning reviewers using Add Reviewer for my submissions, its showing that “Failed AJAX request or invalid JSON returned”, I also attached the screenshot of Network response from browser inspect and the Journal Error While Adding Reviewers.

What application are you using?
OJS 3.3.0-21

Additional information
Screenshot Browser Network Response:

Screenshot Error on Journal Page while Add Reviewer:

[rcgillis]

Hi @scholarsync.projects,

PHP error log messages tend to be more helpful in determining what is occurring in situations like this than browser console logs. Are you (or your systems administrator) able to check the PHP error logs and report on errors found there?

-Roger
PKP Team