Can't unlock Security & Privacy pane

Follow the good advise by @Mal-S and restart in Safe mode.

Use Touch ID on Mac - Apple Support (CA)

If you have problems with Touch ID

• If Touch ID doesn’t recognize your fingerprint: Make sure your finger is clean and dry, then try again. Moisture, lotions, cuts, or dry skin can affect fingerprint recognition.
• If you have a Magic Keyboard with Touch ID: If you can’t unlock your Mac, enroll a fingerprint, or enter your password using Touch ID, see the Apple Support article If Touch ID isn’t working on your Mac.
• If you still have to enter your password: For security, you need to enter your password when you start your Mac. Sometimes you need to enter your password to continue using Touch ID. For example, users must re-enter their password every 48 hours and after five incorrect fingerprint attempts.

dpdpdp wrote:

I am suddenly unable to unlock the Security & Privacy pane. When prompted, Touch ID doesn't work and it doesn't recognize my password. I have an Apple Watch which also asks me to double-click to unlock the pane, but this too has no effect.

I am able to unlock any other Preference Pane by these three methods, with no problem. My username is correct, my password is fine everywhere else, and I am an admin. The issue is isolated to the Security & Privacy pane.

This is a new issue — I had no problems in the past. Any suggestions?

TouchID not working—

There are a few instances where Touch ID will not be accepted by macOS:

• If you restarted your Mac, or if you're not logged into your user account.

• If you have not unlocked your Mac for 48 hours.

• If you are trying to unlock Security & Privacy

• If you are trying to unlock Users & Groups Preferences (when FileVault is on)

• If 5 wrong fingerprint attempts

Use Touch ID on Mac

https://support.apple.com/guide/mac- help/touch-id-mchl16fbf90a/mac

What happens if you disable TouchID and try agian...(?)

Restart in Safe Mode and see if you can access the Security & Privacy pane if yes do a normal restart and check again.

Start up your Mac in safe mode – Apple Support (UK)