Logitech MK550 Manuel D'installation page 15

Troubleshooting
Keyboard and mouse are not working
Check the USB connection. Also, try changing USB ports.
Move closer? Try moving the keyboard and mouse closer to
the Unifying receiver, or plug the Unifying receiver into the receiver
extender cable to bring it closer to the keyboard and mouse.
Check battery installation. Also check the battery power of each device.
(See Battery management for more information.)
On the mouse bottom, slide the On/Off switch right to turn on
the mouse. The Battery LED on the mouse top case should light green
for 10 seconds. (See Battery management for more information.)
Logitech
On/Off switch
Wireless Wave Combo MK550
®
Mouse bottom
English 15