I have recently had to reinstall ADManager Plus from scratch.  I downloaded version 6.3.0 and when I was setting up technicians in the console I ran into an issue when attempting to modify a user.  It doesn't let me edit any users I just receive the attached message in the browser.  I don't have multiple tabs open.  The only work around I have found is to delete the user completely and add them back with the changes I needed to make.

I have attached a screen snip of the message received.