Press ? on your Sky Q remote and check the light on it flashes. If the remote doesn't flash, go to Problems with your Sky Q remote.
If your remote does flash, press Home. If the standby light on your Sky Q box remains on red or amber or is slow to respond, press the Standby button on the front panel of the box.
If your box displays a green light, then the Sky Q remote isn't working with the Sky Q box. Go to Restart your Sky Q box below. If your box remains on red or amber, or continues to be slow, check for ventilation issues.