Hi!!
What kind of error message are you getting. I know from 10.2 to 10.1 your backups won't work. But if you went back to 10.2 i don't see why it wouldn't . Have you rebooted your PC and restarted your phone?
I had to reset both the computer And phone before with link to get a Proper restore done, was advised such after an OS upgrade so would assume much the same for a downgrade!