Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Check whether your HDMI cable is
1. firmly seated, at both ends
2. the ends are quite clean
3. the HDMI cable is of good quality - the poor quality ones often fail.
Also, did you hook up the HDMI connection with both devices Off, turn On the projector, and then turn On the computer and let it boot up? That may be necessary, to get the full display.