Apple Maps, no sound for turn by turn navigation

For several weeks now voice navigation has had no sound when driving with Apple Maps. I hadn't thought about it because I usually do "ETA only" for most trips, and I figured it was just set like that for all trips since I did that for like trips home. But today I realized that there's just no sound coming through at all. I want to be clear about the details of the issue and what I've tried so far:

• I have found that the Apple Maps app has no sound regardless of use method: no sound if plugged into car for CarPlay, no sound if connected to car via Bluetooth, and no sound if not connected to car at all and just using app on phone.
• I have tested other sound things in CarPlay/Bluetooth, and I can hear videos, music, etc. through the speakers just fine. HOWEVER, when Siri is supposed to be reading a text message there is also no sound! It just says reading but no sound comes through.
• I have ensured that Audio is set to play in my car, and that HFP is allowed. Volume is set to "Normal Volume". I also have it set to Pause Spoken Audio.
• I thought perhaps my "Prompt Volume" was too low, so I experimented with that. With CarPlay, background music volume never lowers like it should when a prompt is happening. If just using Bluetooth to have the navigation come through the speakers, then music volume will decrease, and if I try to increase the volume using the car knob at that moment, it just changes "Audio Volume" and the normal graphic for "Prompt Volume" never appears.
• Turn by turn navigation sound DOES work for Google Maps in CarPlay and in the app when not connected to a car.

I feel like I've troubleshooted this a lot and come up with nothing. Not sure why all of Maps sound is affected, and then also Siri's reading of messages in CarPlay.

iOS is 13.5.1 on an iPhone XS.

Car is a 2017 Ford with SYNC.

Any helpful advice or other things for me to check would be greatly appreciated!