Floating or Node Locked licensing?
Could be someone on the IT side changed permissions with or updated FlexLM. I never seen anything like it though.
Found the answer.
For some - still unknown reason - the powerpcb.exe file had been marked with 'Run this program as an administrator'.
I disabled this and then PADS Layout could start without need for user credentials.
None of the users had enabled this checkmark themselves - so we still don't know why this has happened.
But now at least we know how to fix it.