Your boiler has temporarily paused heating because a safety switch, such as the one connected to your condensate drain pump, has triggered to prevent a water overflow.

DIY fix possible

Check if you have an external condensate pump plugged into the wall and ensure it has power.Inspect the clear plastic condensate pipe outside or under the boiler to ensure it is not frozen or blocked.If using a condensate pump, check the reservoir for blockages and ensure the outlet tube isn't kinked.