Be sure the cable into the Dot is pushed ALL THE WAY IN. The plug of the Dot is very tight and you may need to insert/reinsert it a few times before it is looser, and cable jack must be flush with Dot plug.
Also, the receiver inputs you are using should both work, but could be a little "dirty" from non-use so do same with the two RCA jacks. Push all control switches in and out or turn back and forth, etc. This movement should be done annually to clean all switches, etc.
OF COURSE, ALL THIS NEEDS TO BE DONE WHEN RECEIVER IS OFF!