Well, I removed the white plastic piece and tried a test call with the microphone cover completely removed and people still say they can't hear me. What a bummer. Has to be a stealth update that was rolled out because it can't be a coincidence that everybody started having this issue at the same time.

 

For sure could be software although I do notice a marked difference with cover off and cover on that reliably reproduces the issue.
After taking the cover off, maybe try disconnecting your phone and deleting the MB profile from the phone then reconnect. If you’re iPhone, add in the step of resetting network settings before reconnecting?

 

I used a plastic pry tool to remove it. You could also use a flathead screwdriver but I would recommend putting something under it as you wedge the microphone cover up so that you don't damage the liner.

 

2020 S450 W222 same issue Resolved

This is the fix!!!!!!!! Took me 3 minutes to fix, 6 weeks to find this solution. Thank you Sir