The domain troubleshooting guide can help with most custom domain configuration issues. You might be able to use that guide to solve it before a human is available to help you. Then you can come back here and share the answer for bonus points.
You can also use v0 to narrow down the possibilities.
It looks like that site was deployed as a new project by another account, possibly a team member? I can’t share the repository here but you have public commits in it and it’s deployed to a Vercel account owned by the owner of the github repository.