It says the domain was registered through a third party and thus I can’t really do anything (change nameservers, etc).. I’m simply “locked out” of my own domain
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.