Issue resolved.
I first tried clearing and resetting the button. The button was recognized but the PTT still did not engage. I then changed the Win10 sound setting from default to the headset being used. That did not solve the issue either.
Then I reset the button in P2A config on a different hardware (the yoke this time). That worked. Then I reset the button back to the original hardware button that was previously not working. It now works.