To factory reset a Wireless Radiator Valve requires taking it off the radiator and taking it back to the Genius Hub.

To factory reset a Radiator Valve

• Remove a battery
• Press and hold down the middle ('o') button
• Re-insert the battery
• The valve will perform a screen test
• Keep the button pressed until the screen goes blank

The Valve is now in a factory reset default state, to add it back onto the system again see this link.