are you sure it doesn't work?
Where did you test it? on one PC or a few?
Just wondering if its a software cause perhaps?
Try a clean boot and see if it changes anything - make sure to read instructions and make sure NOT to disable any microsoft services or windows won't load right -
https://support.microsoft.com/en-au/help/929135/how-to-perform-a-clean-boot-in-windows
if clean boot fixes it, it shows its likely a startup program. You should, over a number of startups. restart the programs you stopped to isolate the one that is to blame.
I don't see anything specifically about fixing the capture key. It seems strange its just 1 key. Sure it doesn't have fluff under it?
Which button is it on keyboard? Along top or one of the ones inbetween the 2 rows of keys?