I’ve seen two answers to people experiencing this issue.
You can try this:
If it’s unavailable or doesn’t work, then it’s likely you have been banned for whatever reason, as per:
https://answers.netlify.com/t/i-cant-login-my-account-after-register/98082/2
If that’s the case your best bet would be seeking another provider.
Impacted users linked to other providers in this thread: