First of all, please ensure the lamp is inserted correctly and all screws have been fitted back on.
Please check how many times the power and lamp LED lights flash. The flashing sequence usually provides an error code related to a certain fault.
You can check the meaning of different LED sequences on the projector’s User Guide. To access it, please go to http://www.prometheankb.com and search for 11119.
You can also disconnect the power cable, leave it for 1 hour and connect it back again, then check if the issue still persists.
Please let us know if you require further details.
Promethean Technical Support (support case #561784)