Your boiler has lost its connection to its internet or remote-control gateway, so it may not respond to app or thermostat changes, though it will often keep heating your home.

DIY fix possible

Switch the boiler off at its on/off switch and at the fused spur or isolator, wait 2 minutes, then switch it back on to reset the communication.Check that the gateway unit (the small box connected to your router) has power and that its network cable is firmly plugged in at both ends.Confirm your home Wi-Fi or router is working and that the gateway is still connected to it, then restart the router if needed.If the code returns, leave the boiler running and book a heating engineer to check the gateway and communication cabling. Do not open the boiler casing.