old xbox accounts not getting gamertag reset

There's no way to know for sure how inactive an account is. The gamertag system is in use on other Microsoft services, so even if it's no in use on an Xbox, it may be in use elsewhere.

I'm Sorry but there is no way to have a gamertag to be reset. The tag system is use on other Microsoft services, so even if it's not being used on the Xbox 360 or Xbox One, it could be used elsewhere. If the gamertag is taken there's no way to request a
reset of that account even if it appears "Inactive." There might be a reset of some old inactive gamertags sometime in the future, but until then not much you can do.

Hello YummyCanadian! The problem you might be encountering is last year or the year before Microsoft reset tons of unused and banned gamertags. I'm wondering if your gamertag was reset in that program. i had an old gamertag from when i had my Original xbox
that i was never able to recover, but when the tags were reset i was able to create a new account with that same gamertag because it was reset. Try and create a new account on your console. You will be able to change the gamertag once free of charge, see if
the gamertag you had was reset.

Does anyone know when is the next gamertag reset for old OG user name accounts?

Not exactly sure what your asking?