Cryptopia is old and has the same standard early exchanges have till today. And the customer care is worst.
But for your problem, first be sure whether they are asking for google 2FA or email code or OTP.
If not for some rare coins not listed in other major exchanges, I've dumped cryptopia in favor of others.
Yup, I had the exact same issue... Email code on old account was telling me I was entering the wrong 2fa... Turns out the codes were just arriving in spam...
The support helped me reset my password regardless, although it took a couple of weeks. Overall, I'd say it's an average exchange. Not the worst but not the greatest eiter. Could use some renewed infastracture but I guess they're of the mindset 'if it ain't broken, don't fix it'. They are a small team I think.