Help me Troubleshoot Google Ads Login

Hi, I'm looking for someone who could help me troubleshoot with Google Accounts / Google Ads. I've had a private Google Ads Account, which I didn't use for a long time now. I recently founded a company and therefore I'd like to setup a new Google Ads Account. I've deactivated the old account and registered one with my Business Email Address. It went all through and have been in the backoffice with the new account. But now I can't login again, I always get the Error message about the cookies. I've deleted all cookies from the past 4 weeks, but I still can't login with the new account. Login with the old account works, so I don't think that the problems are the cookies. If you might help, please let me know as soon as possible. best regards, Roman