If the keys on a mechanical keyboard fail to function, it may be due to the following reasons:

Stuck keys or loose springs: If a key gets stuck or the spring becomes loose, the key may fail to return to its original position, causing a malfunction. In this case, gently tapping the key or using a thin tool such as a toothpick or scissors to pry open the key and check if the spring is normal may help.

Loose or damaged keycaps: If a keycap is loose or damaged, it may fail to trigger, causing a malfunction. In this case, blowing the dust and dirt out of the keyboard with a hair dryer or replacing the keycap may help.

Keyboard connection issues: Poor keyboard connection or cable damage can also cause key malfunctions. In this case, checking whether the connection is loose or replacing the cable may help.

Driver issues: Damaged or faulty keyboard drivers may also cause key malfunctions. In this case, reinstalling or updating the keyboard drivers may help.

If none of the above methods solve the problem, the keyboard may need to be repaired or replaced.