Q: 'Call Failed' Macbook from FaceTime Audio

If you're connected to the same network with both Ethernet and Wi-Fi, please either turn off Wi-Fi or unplug the Ethernet cable.

Open the Sound preference pane and select the Output tab. Select Internal Speakers from the list of output devices, if not already selected. Test by adjusting the volume slider; you should hear an alert sound.

Next, go to the Input tab and select Internal Microphone as the source, if applicable. If your model (mini or Mac Pro) doesn't have an internal microphone, select an external one that you connected. Test by speaking into the mic; you should see a response on the Input level meter.

If you made any changes to the sound settings, try FaceTime again. Otherwise, sign out of FaceTime on all your Apple devices, including iOS devices if applicable. Log out or restart the computer. Sign back in to FaceTime and test.

Same exact thing here on a Mac Mini. It is apparent that Apple broke something recently.  I've TRIED EVERYTHING and yes, I'm enabling everything correctly.  Trying to make/receive calls FAILS when it is by Mac/Phone only through Wifi, but it works occasionally when both are set to make/receive calls wifi or when not nearby -- although the voice on the other end sounds like Micky Mouse.

Apple broke something and, being Apple, they won't admit to it and ignore it like the problem doesn't exist.

With the update today, Apple didn't COMLETELY fix this issue, but there is a step in the right direction.

Facetime Audio (calling/receiving Mac <--> iPhone) seems (so far) to be working (not verbatin for language, but) "When phone is nearby or away".  It even works with iPhone's WIFI turned off just over LTE.  I'm assuming the calls go through the iCloud to do their magic.  THIS IS NOW WORKING (so far it seems).

HOWEVER, (oddly), it STILL isn't working "use your iPhone when your phone is nearby and on same wireless".  This STILL results in "CALL FAILED". So, I'm assuming, its not going MAC <-WLAN-> iPhone, but it IS going through out through the internet  MAC <-iCLOUD-> Phone. You would expect the latter to possibly have issues, but not the former.  However, that is what I've been getting (and able to REPLICATE).  I DONT want to use it as MAC<-iCLOUD->PHONE, I WANT to use it as MAC<-WLAN->PHONE.  I don't want my Mac to ring everytime I get a call when I am AWAY form home. I just want to use this feature locally, but it is not working -- and I have tried EVERYTHING possible to fix it.  Something is off somewhere, perhaps maybe even just a file permission somewhere got corrupted, but its somewhere deep within the OS.