Hi, this is a frequent issue that keep popping up when I am using photoshop.
The brush will completely lose it pen pressure sensitivity completely, most of the time I will have to switch out to (tap another program) to regain the sensitivity though there are times where I need to complete restart my PC to get it back.
This issue had been ard for quite a few version, and I encountered it on a completely new PC with different wacom models (so it couldn't be an hardware issue) also, none of the other programs that uses the pen pressure sensitivity never encountered this issue at all.
My system is running Windows 10 (it happened on my previous Windows 7)
My wacom model is a Cintiq 16
And current photoshop version is 23.2.2 and using Wintab drivers as the Windows Ink drivers is completely broken