Power on, loud fan noise and no screen

When I powered on to update the fan came on very loud and there is no screen, not even any output from the projector, as if the light source is not working.
I’ve tried powering on and off (I have to hold the power switch down for about 10 secs to power it off).
Unplugging it and removing the HDMI feed followed by power cycling, unplugging etc.
Any ideas?
Thanks.