Press the pairing button on your mouse or keyboard for 5-7 seconds, then release the button. If the light flashes, the mouse has power. If the light doesn’t flash, check the batteries or replace them.
Open the battery compartment on your mouse or keyboard and make sure the batteries are inserted properly, then see if it works. If it doesn’t, replace the batteries with new ones.
Note: Some devices have rechargeable batteries. Use the USB cable that came with the mouse or keyboard to recharge them.