DL-3F: proj comm error

Projector answers to remout control, so it is alive. Physical connectors are secured.
DL-3 answers to HOG4 commands, even shows content to built in display, but not via Proj.
What can be a source of the ERROR?
P.S. rebooting, reset to factory defaults - have no effect.
I could start a show with this error after manual powering projector by remote control, but projector doesn't power up via DMX command.