It's pretty a straight forward process, but there can be hiccup for some.
Firstly, make sure you use a Chrome browser to do this. Secondly, make sure you are using a real service pack screen. Then we can proceed.
Step 2
Follow the instruction on the page.
Step 3
Turn off the device, enter Fastboot mode.
Connect the phone to PC.
Step 4
Select Pixel 6 and accept the connection on browser.
Step 5
install the software.
Step 6
Wait while it does it's job.
Step 7
Once it's finish, the phone will restart.
Test the fingerprint now.
Note Again: It only works with Service Pack screen and Google Chrome Browser.