Face ID unavailable

Hello sir/Madam

So after updating new IOS 15.4.1 into my iPhone 13 pro. It than showed me its new features along with using face ID while wearing mask and suggested me to try it and I did but after that it won’t recognise me every time when I unlocked it so I reset it but then when I tried to set it up again it always showed a notification that it isn’t available and try later when my iPhone warms up. What to do ?