win10 upgrade stuck at key request

I have three computers in family that were given upgrades on the win7 family plan. One was just informed it was eligible for win10 upgrade. I think I made the mistake of custom install (for a clean install) instead of an upgrade and, related to other problems with windows update, I might have lost my activation on win7. Long story short, when I got to the point where win10 was installed and asking for a key I knew I had done a no no as, if I had done it correctly, I should not have been asked for a key. Of course I have no key but the win7 key and the install just sits there with no options but to input the key, which I don't have. What's my best course of action here?
thanks in advance

I tried every key I possessed. Vista, win7, win8.1. Install just says not a good key. Maybe because it is expecting a full retail key instead of on upgrade key.

Since I got that far what's my best approach.

Reset and see what happens.
Retry the 10 install only this time opting for an upgrade and not giving a key again until seeking activation? or if all goes well I might not even be asked for a key?

I may just try to revert to the win7 install, check if it is still activated and if so, proceed with the upgrade.