Hello jterry5472,
Welcome to Apple Support Communities!
We want to help get the microphone working as expected when using FaceTime on your iPad Pro.
Even though the title of this Apple Support page doesn't exactly match the issue you've explained, it still has the best steps to take for an app related issue: If an app on your iPhone or iPad stops responding, closes unexpectedly, or won’t open - Apple Support
See here:
"If an app on your iPhone or iPad doesn't work as expected, try this.
- Close and reopen the app
Force the app to close. Then open the app to see if it works as expected.
2. Restart your device
Restart your iPhone or restart your iPad. Then open the app to see if it works as expected.
3. Check for updates
To see if updates are available for the app, open the App Store, tap your profile icon, then scroll down to see if updates are available. If updates aren't available for the app, update the software on your iPhone or iPad.
4. Delete the app, then redownload it
Delete the app. When you do this, you might lose data that was stored in the app. Then redownload the app. Then check to see if the problem with the app is fixed."
If the issue continues, is this a managed device? Do you have parental controls enabled or a managed profile installed? Do you have any connected or paired devices? Do you see any errors?
We hope this helps to further isolate the source of the issue with the microphone.
Cheers!