Diagnosis
The projector is failing its power-on self-test, most often due to a failing or overheated lamp or a power supply issue.
How to Fix It
Unplug the projector, wait 10 minutes for it to cool completely, then plug it back in and try powering on. If the red light persists, the lamp is likely at end of life or has failed. You'll need to replace the lamp assembly.
If That Didn't Work
The internal power supply unit might have a fault. This requires professional service; contact Optoma support.
Heads Up
Never touch a new lamp's glass with bare fingers; skin oils cause hotspots and premature failure.