I'm not associated with that registry, so I can only generalize and guess-timate:
Have you contacted TN's nurse aide registry about the possibility of transferring your registration there? Ideally they could give you the best explanations.
Keep in mind that each state's nurse aide is registry is different, and maybe some aren't open to other-state transfers for reasons only that registry can offer.
One possibility might be that TN requires a certain standard or certification of CNA training that other states may not necessarily include in theirs. (Something comparable I see is MD transfers to WV; MD nurse aides need a GNA certification before they can be accepted to WV.) If transfers are not accepted, (re)training is perhaps the alternative to attaining the appropriate skill level or standard for their state.
Is your NC certification current/active/in good standing? If its out of date for too long, is retraining necessary to bring it up to speed? Is an active certification required for a transfer to TN?
Again, these are just a few guesses from someone on the other side of things. The best thing to start is with TN's registry to see about their policies on transfers and/or training. If you need to check on your NC registration, consult NC's registry and follow their procedures if necessary. The pushback is not necessarily personal, even if it doesn't make sense. Ultimately, either and all state registries are operating on local and/or federal laws/mandates/policies/requirements/etc. set for them.