Have you tried the SMMI test to check if fingerprint sensor working or not?
Via calculator .12345+= check if fingerprint sensor passes the test!
Also most likely if the fingerprint scanner hardware is damaged the option disappears or seem disabled in software settings.
Have tried this with other Rog phone when the hardware is detached from the main board setting option disappear or appear disabled. But as it as the hardware flex is attached back it works and shows in settings.
If you have done basic troubleshooting try factory reset even if it doesn't work then it could be a hardware issue and not the software.
