If you are hearing audio but no picture unplug the receiver for 10 seconds and plug back in. This will reset the receiver and it will reboot itself for you once plugged in. This should resolve the issue, but if you continue to experience problems please e-mail me at nick.franta@dishnetwork and we may need to replace the receiver.
Are you receiving any error messages on the screen? Usually with signal loss it would be error 015 or 002. I would suggest during a hard reset with the receiver by unplugging it from the wall for 10-15 seconds and allowing it to reboot once plugged back in. If the problem persists run a check switch test by hitting menu on the remote followed by 6-1-1. If you receive any error messages after the check switch we will have to send a technician out to correct the issue. Feel free to e-mail me at firstname.lastname@example.org with any further questions or concerns!