* check your warranty. call for support. (Projector first, then DVD player.)
* Brand and model for specific solutions.
* Check your DVD menu for "Output to HDMI"
* Check your projector for "HDMI INPUT" is selected.
* Check using a TV monitor if you still can get a signal from the DVD player (using the HDMI TV input)
* check HDMI cable (they damage easy) look for bent pins.
* Note; double check if the HDMI output from your DVD is the compatible with your projector. ( there ar 4 types of HDMI ); https://en.wikipedia.org/wiki/HDMI