Hello everyone,
I too am experiencing the problem - I updated from 13.6.1 to 15.3.1 - I purposely waited so long because of all the problems reported (Forbes.com).
I've now got multiple issues that are "intermittent". I've got an iPhone 8 and a Chevy Cruz 2018. When I press the "voice button" on the car console to make a phone call (i.e. Call Home), Siri hesitates and then says "there seems to be a problem, please try again" - well you know that never works out despite repeated attempts.
Also, using voice commands from the Gmap mic icon on carplay doesn't work at all. (Yes, I've got Siri voice enabled).
*The worst bummer is I no longer get the "turn by turn" audio instructions while driving - but I DO get a "BOOP" sound (which I found is the indication that there is an instruction or turn coming up - but for some reason is not able to be played).
My mom is in the hospital (I know, not relevant), so I have not been able to "fully" experiment with all the suggestions - but toggling on/off the bluetooth options (from within the Google Maps app>settings>Navigation>play voice over Bluetooth and Play as Bluetooth call) didn't make any difference.
Perhaps most frustrating is that those turn by turn instructions can "suddenly start working" while driving. I was coming home from the hospital and getting only the "BOOP" tone before turns, then as I near my home, the voice suddenly started working, "turn left in 100 feet" - and it continued to work right up to me pulling up to my garage.
Needless to say, like all of you folks, not having audio instructions is a nightmare. And why both voice calling and Gmaps voice commands are "intermittent" without any re-producable settings/changes is upsetting, to say the least.
If anyone could comment or help me, I would be very grateful. Thanks to all. (my first post to the forum in case you haven't guessed-lol).