Over the last couple months, I often run into issues were the TouchID dialog will not display when unlocking the touch Macbook Pro. It will also not display as an option when installing software other options. You are forced to enter your password. I was only able to get it working again by rebooting.
Today I finally figured out how to fix this without rebooting.
- Go into System Preferences -> Touch ID
- Check or uncheck the boxes under "Use Touch ID for".
- When you check or uncheck either "Apple Pay or iTunes & App Store", you will be prompted for your password. Enter your password.
- Finally, reset the checkboxes to how they were before.
This will (I assume) restart the Touch ID service and it should start working again.