Facetime not answering on iMac?

Hello,
Issue is simple. Facetime won't show or answer calls on iMac.
I turned my phone off to make sure it would not answer.
Checked that all settings are OK.
Checked phone settings and iMac settings for Facetime.
Logged out and in of Apple account.
Checked region, date and time.
I can call and it works but when the same persons calls back nothing happens on my iMac.
In some cases I have a valid iCloud ID to call but Facetime can't do a video call.
If I open the phone it will work.
My problem: I am using Screeflow to do a recording so I need Facetime to receive the call on my iMac.

I can test it since I have an iPad with a different Apple account.

This is a first as it always has worked without problems.
I didn't update OS and still using Catalina latest.
Is it possible to uninstall Facetime and reinstall it?

Thanks.

Is the incoming call coming via mobile?

No. It is actually done from an iPad.
Just now I managed to do it using my Macbook air.
A bit less screen but still fine.
Mystery...of my IiMac.