A multiswitch allows more than one receiver to watch something on the satellite. In my case I have Directv with the three LNB dish. The multiswitch I have will allow me to hook up to 8 tuners to watch something on each at the same time.
Not sure why you would be getting errors. What does it say specifically?
How many receivers do you have?
Also how many dishes are on the roof?
The common reason you would have a multisiwtch
-more than 2 receivers (since the installer probably used a Dish Twin and switch)
-Superdish (3 inputs from the satellite)
-2 dishes (same reason as Superdish)
They're just the basic generic error messages saying I need to test the multiswitch before I can view or change channels on the 2nd tuner or something like that.