It’s a known bug that with the recent Windows10 update (type 2004) the sensor did disappear and won’t work. Welcome to the club Chuwi won’t fix it, and most likely Microsoft doesn’t even know anything about this issue.
I was able to solve this problem, though I don’t understand what the root cause was. Something (maybe a bios update?) caused the hardware id of my fingerprint reader to change. The Unknown Device that showed up in device manager had a Hardware Id of ACPI\FTE4800:
If you look at ftwbioumdfdriverv2.inf from the Chuwi provided fingerprint reader driver, you can see that it expects hardware Id ACPI\FTE3600 on line 17:
I changed line 17 to reference the ACPI\FTE4800 value from Device Manager and was able to install the driver normally (though I had to enable unsigned driver installation, since I modified the driver files and thus broke their signature).
Not sure why this happened, but glad to have the fingerprint reader back!