Hold the power button down on the dishnetwork Receiver for 10 seconds to turn the unit off. (not the remote control).
This should perform a HARD boot reset.
It should come back on within about 30 seconds.
If it does not. Hold it down for another 10 seconds and it should eventually come up.
It should progress through the normal aquiring satelites message and the start the 1 of 5 etc.
Make sure that the cables are Tight on the DISH and also on the Receiver.
Also make sure that the connectors are tight at the ground block which may (or should) be installed right before the cable enters the house. (it looks like a splitter that oes not split).
If you wish, you may disconect a cable one at a time so that you do not forget exactly where it goes and check to see that the cable end is clean and not corroaded. Also make sure where the cable connects to is also clean and not corroaded.
Sometimes the sheer act of unscrewing it, taking it off, and putting it back on with fix and bad connection. (which will also fix a can not fins sat problem).
Do you have a surge protector plugged into the receiver. I would do that ASAP.
This will filter out power line noise and also protect your receiver.
If it continues, you will need to call dish network and let them know of the problem. The dish may have been moved by high wind or heave rain or snow or eath quake, or kids climbing on the roof, etc.
It may need to be reaimed.
If you do not have the $6 per month protection plan from dish, now would be a really good time to sign up for it. BEFORE you schedule a service CALL.
Take my word for it, you will get all your money back on the first visit.