Hello,
I had the same problem and I have solved it. I have a Rift S working about 1 year ago and suddenly this problem came up a few weeks ago.
I have tried:
-Reinstall NVidia graphics drivers
-Reinstall Oculus
-Other USB ports
-Reconnect the HMD connector
Nothing has worked, so I thought about reverting the NVidia drivers, installing an old version. It's the solution.
I have an RTX 2060 and downloaded the drivers from two months ago:
446.14-notebook-win10-64bit-international-whql
Just download the driver for your graphics card, from about two months ago and it works! Even without restarting PC.