Home App / HomeKit not working remote on iPhone 12 AT&T 5G

Hi,

I have Home App (HomeKit) with many devices that I use to be able to control remotely on my iPhone 11 Pro. Just got my iPhone 12Pro on AT&T, upgraded my data plan for 5g and now I can not access any device in the Home App. All devices say No Response.

I have googled searched high and low, done all the recommendations (log out and back into iCloud, make sure all hubs are reset, log out back in. (BTW, this is a PAIN to have to re setup everything). I've reset network settings on my iPhone 12. Nothing.

Now here is the odd thing. My wife's iPhone 11 Pro has zero problems connecting to the HomeApp while on Cellular data (AT&T LTE).

There is something not right with AT&T 5G and the iPhone 12 Pro.

Side note.. I have a Tesla, and the Tesla app does not work on Cellular data either (5g) but does on my wife's phone. There are many other Tesla owners with the same problem on AT&T 5g and new iPhone 12.

Any thoughts or suggestions on how to diagnose or resolve further?

Thanks,

mike