Look forward to hearing what they say, if you can get them to understand it.
This isn't much help, but I noticed the it's logged locally here:
Microsoft-Windows-DeviceManagement-Enterprise-Diagnostics-Provider/Admin
"MDM Enroll: Certificate enrollment request sending failed. Result: (Unknown Win32 Error code: 0x80192ee7)."
It's just not making the connection, as if there's a fundamental problem--which would make slightly more sense if I couldn't then immediately make it work with another tenant. Figuring out why that is will be the answer.
I should point out that we don't use Intune, so our MDM, if you can call it that, is just the base Microsoft 365 one. I suspect they're in the same boat when it comes to this problem though.