It may see a bit cliché, but turning your router, even if it's as awesome as an eero, off and on again really can help.

If your eero light is red, follow the guide in our article - There's a red light on my eero

Otherwise, just remove the power, either by switching it off at the wall or by removing the power cable form the back of the eero.

Give it 10 - 20 seconds before plugging it back in, then wait a couple of minutes until it boots back up.

If you want to know what the colours on your eero mean as it boots back up, there's an article for that - What do the colours of the LED light on my eero mean?