Getting Started Guide
Page 15
Also, try changing USB ports. The Battery LED on Mouse bottom the mouse. Check battery installation. Logitech® Wireless Wave Combo MK550 Troubleshooting Keyboard and mouse are not working Check the USB connection. 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... check the battery power of each device. (See Battery management for more information.) On the mouse bottom, slide the On/Off switch right to the keyboard and mouse. Move closer?
Also, try changing USB ports. The Battery LED on Mouse bottom the mouse. Check battery installation. Logitech® Wireless Wave Combo MK550 Troubleshooting Keyboard and mouse are not working Check the USB connection. 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... check the battery power of each device. (See Battery management for more information.) On the mouse bottom, slide the On/Off switch right to the keyboard and mouse. Move closer?