There might be some reasons:
1. The lens in the internal light path of the projector burns out, resulting in the inability to project the picture.
2. The internal temperature of the projector is too high and the self-protection mechanism is activated resulting in no projection.
3. The projector has selected the wrong signal source resulting in no picture.
4. There is a lens cover in front of the projector lens that is not opened resulting in no picture.