This can sometimes happen if you're logged in with the wrong Microsoft account. Please try logging in with a different Microsoft account, just in case it was migrated somewhere else on accident. I usually recommend trying the same email that you used for your Mojang account. ^NS

Only one Microsoft account was used. I believe that the process was interrupted when I updated my Microsoft account information. Afterwards, the account failed to migrate, but it was still deleted which is why I can’t log in normally on the Mojang website.