Were you selling in more than one Marketplace? If so, did you delete one of them or ask Amazon to delete one? Or did you delete your buyer account associated with your seller account?

If your answer is no to all of the above, try the usual trouble-shooting advice: clear your cache, cookies, restart your device, try a different browser or a different device. When I say try a different device, make sure it doesn't belong to someone else who also has an Amazon account and uses it to log in to their account. Using a device another seller uses will link your account with theirs, which is a whole other problem. It should be a different device you own that no one else uses.

If none of that works, try the Seller Central Technical Support Page You should be able to access that without being logged in. Ideally, it would be better to open a case directly with Seller Support but if you can't log in, you won't be able to do that.

Try tagging a couple of Community Managers to see if they can assist.