Welcome!
This issue is common when a GitHub account is accidentally linked to a new Vercel account. To resolve this and restore your old account, follow these steps:
Disconnect your GitHub account from the new account:
Log in to the new account you recently created.
Go to Account Settings, then Settings or Billing/Tokens (depending on the interface), and unlink or remove the currently linked GitHub account.
Log out of the new account completely.
Log in to your old account via GitHub:
On the Vercel login page, click the Continue with GitHub button.
Since your old account was linked to your original GitHub account, the system will recognize it immediately and restore you to your old account and previous projects, regardless of the old email address (as long as you are logged in with the same primary GitHub account you initially used to create the projects). Opening support tickets (if necessary):
If the problem persists, you can contact Vercel support by creating a new support ticket from your alternate account or by sending a message to the support team to update the email address for your old account after verifying your ownership of the GitHub repositories.
I hope you recover your account and projects soon!