I have posted this same message before but didn’t get any answers, the only answer I got suggested that I may not be promoting the deployment to production, but after I checked it, I can confirm that all my deployments have always been pushed to prod.
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.