Logitech K750 Troubleshooting Manual page 7

5. After your system restarts, open SetPoint to verify that My Keyboard tab is available.
Contact information:
If you're still having the same issue, see
Logitech Technical Support.
K750 keyboard battery light does not stay on
The battery indicator lights on the K750 are not intended to stay on. This is the normal behavior
of the keyboard.
When the keyboard is first turned on, one of the battery indicator lights next to the Check-Light
button (shown below) will flash:

Green light
If it the green LED flashes, this means the battery level is good.

Red light
If the red LED flashes, it means the battery level is low.
To conserve power, neither battery indicator light will remain lit after the initial signal
K750 LUX number low even in a well-lit room
Knowledge Base article 20596 for how to contact