On your iPhone, go to Settings > Apps > Phone > Calls on Other Devices, ensure the setting is on and your Mac is turned on under Allow Calls On.
Make and receive phone calls on Mac, iPad, and Apple Vision Pro - Apple Support
On the Mac, sign out of then back into your Apple Account.
Have you rebooted your Mac? If not, that's the next step. If that does not help, then see if the problem is present when you boot in safe mode. That process performs some system cleanup and clears caches, andalso disables 3rd party extensions that may cause problems.
Start up your Mac in safe mode - Apple Support
If that does not correct the issue, test in a new user account. A newly-created user account will have all settings at default, and if the issue does not occur in that new account then it provides guidance on what may need to be changed to correct the issue.
Add a user or group on Mac - Apple Support
Once the testing is complete, the new account can easily be deleted.
Delete a user or group on Mac – Apple Support
Those steps will help to isolate the problem.
It might help to download and run EtreCheck, written by a long-time forum member. The free version is fine. Post the full report using the Additional Text button. No personal information is revealed.

Personally, I get calls to my iPhone on my Mac running macOS 27 Golden Gate (and on my iPad, Watch and my other Mac running Tahoe…all at the same time), so this does not appear to be a bug with Golden Gate.