Hi Lauren Lackey,
Thank you for reaching Microsoft Community. I'm sorry to hear about the fingerprint issue that you are having on your Surface.
Please confirm first which Surface Laptop model do you have? You may enter the serial number here to confirm: Check Warranty Page - ROBO SelfServe Portal (surface.com).
Just to make sure that I get the correct picture of the concern: the issue only occurs intermittently and there are times that the fingerprint scanner works fine, correct?
When you go to Windows Settings > Accounts > Sign-in options when the issue occurs, is there any error message displayed under Windows Hello Fingerprint option? If yes, please share the message.
For now, kindly run these steps first on your Surface then observe if still the issue persist:
1: Run Surface Diagnostic Toolkit
See: Fix common Surface problems using the Surface Diagnostic Toolkit (microsoft.com)
2: Check for Windows Update
Go to Windows Settings > Update & Security and select Check for updates
Make sure all updates need are installed including Optional updates
3: Run System File Checker Tool
See: Using System File Checker in Windows (microsoft.com)
Kindly check also and confirm in Device Manager, under Biometric devices if Fingerprint Sensor is installed.
Kind regards,
Marrion