What can I do about it?

I bought an FN account from MMOGA. Since the ACC is for XBOX, I'm logged on to the Epic Games website. Now I wanted to link the account to Switch via Epic. But a verification code was sent to the email address. However, I only have the Epic Games data. When I use it to log into Gmail, the password is wrong. I don't have a phone number from this ACC either.

Then ask him if he can confirm the email

OK