All devices can access Apple Home when away from home, but one Mac can not

For all my devices, I have as far as I can remember never had any problems accessing HomeKit/Apple Home when away from home. The last few weeks, however, a MacBook Pro has stopped being able to see/change the status of my home devices (everything grayed out and "no response").

I don't know that I made any changes that should trigger this, and rebooting the Mac and playing with turning on/off vpn has not helped. I have been hoping that the upgrade to Tahoe might "shake it" out of this, but sadly not.

I have also tried turning off/on Apple Home in the iCloud settings on the Mac, but no luck.

With a different Mac, an iPad and two iPhones having no such problems, I cannot see how the issue can be on the "home side" (router, Apple TV).

Any ideas how to remedy this?