The battery is not properly inserted into the battery compartment or is depleted.
Check whether the battery is correctly inserted in the battery compartment.
If it is not, correctly insert the battery.
If the handle is still not working, replace the battery as follows:
Open the cover to the battery compartment using a screwdriver, for example.
Remove the battery as shown in the illustrations. Please note that the location of the battery holder may vary depending on the appliance.
Replace the battery with a new one. Make sure the polarity is correct.
Then reinstall the cover.
Dispose of the old battery in a designated recycling bin for batteries.