adobe premiere elements 15 serial number does nothing

i have this weird issue where I used this program for a year or so. but one day it asked out of the blue my serial number in a pop up-window, didn't think much of it, and kept editing like normal.

but the next time i reopend premiere and loaded my project, the same window popped up. but this time i couldn't get around this, so I filled in my serial number, then it just closed, and the same window popped up again! so now i can't license the software anymore, and i can only use the trail version.

i tried reinstalling it but that didn't help either.