We have found that companies whose employees do a lot of work with their hands--or wash their hands frequently--sometimes have had issues with the machine reading their fingerprints.
These are the solutions we have found work the best:
1. Have the employee type in their ID number then press their finger against the glass. (They should not press M, either before or after. Just type in the number, then press the glass.) This makes the machine compare your fingerprint against the one(s) they have in memory for that specific employee, rather than try to find it among all the other employees' fingerprints.
2. Puff on the finger, as you would cleaning your eyeglasses. A very dry fingertip makes it harder for the machine to get a good read, and your breath adds a little bit of moisture to the finger.
3. Clean the glass.
4. Reduce the threshold for a match. This is a last resort, because it can produce false matches. It makes the machine be more lenient about what it considers a match. If the threshold is set too low, it can result in one employee's finger being mistaken for another.
Menu > System > Fingerprint
Original Firmware (Series 10 and Older Series 800):
Menu > System > System
Threshold 1:1: 15 (default) > 10, minimum 5
Threshold 1:n: 35 (default) > 25, minimum 15
Sensitivity: Low / Mid (Default) / High > no need to change unless clock is not responding at all
If none of these steps work, and if it's just one or two employees, you can try reenrolling their fingers, or enrolling another finger. In extreme cases, you may want to assign them a password or an RFID card to use instead of their finger.
Lastly, if the clock is damaged, we can replace the fingerprint module. Please let us know if you would like to try this option. We can provide pricing.