Your boiler is currently in the process of being filled with water, and the control system is waiting for the pressure to reach the correct level before it can start working again.

DIY fix possible

Locate the filling loop (a flexible silver hose) underneath your boiler or near your pipework.Gradually open the valves on the filling loop to allow water into the system.Monitor the pressure gauge on the front of the boiler until it reaches the green zone (typically between 1.0 and 1.5 bar).Close both valves firmly once the pressure is correct.