I found a UK thread about this that isn't flattering for Samsung and I found a similar problems on another device and I am still pulling my hair out.
I can make calls fine BUT google assistant, samsung keyboard, and bixby all don't pick up my mic at all. For example, if I try to voice train Bixby or Google, the animation doesn't indicate it's picking up anything and it responds that it "didn't get that". I don't have an unusual accent for Ohio and my home google system works fine and responds to the same commands I try to make to the phone as I fiddle with my phone. Once again, I CAN be heard crystal clear on phone calls on the phone app and apparently google voice when I make a call. This problem also extends to the tapping the microphone icon and trying to speak in the google search bar, even the one built into settings.
APPS EFFECTED: Google Assistant Bixby Samsung Keyboard Samsung Voice Recorder Pretty much everything but below hypothetically
APPS UNEFFECTED: Phone Voice
THINGS I'VE TRIED: wiping partition cache from safe mode full factory reset (Tried before any installs, no luck) cleaning the microphone hole checking microphone permissions for each app(edited) curse words
It had worked fine since I got it, I use "Hey, Google" for everything including work, because I drive a van to doctor appointments for a rehab center, so this is getting very inconvenient with Ohio's new "Don't touch your phone" style law. I even broke down and tried Bixby even though I'm not used to it and it doesn't work either. I think there was an update recently but I don't think it stop working right after it. I had been a few days first.
If the microphone is still not working correctly, then it is recommended to have the phone evaluated by an authorized service center. You can use the following link to find a list of service centers near you that can do the repair: http://www.samsung.com/us/support/service/location or by contacting customer support at 1-800-726-7864.
