Depends how old the account is.

If this is an account from like 2015 that you haven't used then those might be had too many login attempts from Bitcointalk forum.

Many people out of laziness just reused the same password and got all their emails and other crypto assets stolen.

The ones that were lucky and used a different password were ok but if there are too many login attempts the site will block it for your protection.

Primedice isn't the only crypto service that does this. Many exchanges do this. Hence you are better off using a unique email and unique username for all the major Bitcoin services that you use to avoid this headache.