How can you improve Face ID Face ID fails to recognize me 90% of the time on iPad Pro.

How do I know why it fails. What can I do to make it work?

I have read and done everything that's mentioned in Apple Support document, If Face ID isn't working on your iPhone or iPad Pro.

How, at least immediately after saving a Face ID scan can I check that it works, i.e. test Face ID say 10 times.

Now it seems to unlock from wake-up and is working about half of the time and in apps e.g. App Store not working at all - How can I keep retrying so it learns?

have just got a useful message from an app - saying that Face ID had failed 5 times so I need to reenter the apps password.
In this case it was the distance between face and ipad. Apple says 10-20 inches. I need it to be more than 20 inches to get 60% working on wakeup which is difficult when I can only read the message to use Face Id from less than 10 inches