Windows Hello, BIOS setting, PTT on fix

I start this in case it helps someone.... 

Windows Hello and Pin stopped working after hours with Microsoft support we eventually got the Pin to work by creating a new account but not Hello. It whent through the motions of setting up if no Pin was set but it then asked for a Pin, I set a pin but then nothing saved. If a Pin is set before setting up Hello you don’t get the option to start face recognition. I eventually looked at Bios after reinstalling a SSD I had upgraded 3 weeks earlier expecting it to work (it had worked ok for almost a year) but no it came up with same pin and Hello issues. This ruled out any windows update etc.

Dell inspiron 7-7779
for me the resolution was to go into BIOS setup (F12 on bootup) open security tab and select PTT Security and select PTT (Platform Trust Security) ON.

i rebooted and setup Hello, it let me set it up all ok this time.
i have rebooted several times and each time it has recognised my face and signed me in.

I Assume some update Bios or other had switched it off.
i also assume that a similar fix would work for other systems, all be it the details may be different but checking your BIOS would be a good place to look.

I hope this helps you fix your problems.
would be interested it this is a Fix for all

regards John