The dish pulls in multiple satellites. So it's possible for it to be out of alignment but just barely still pulling in one of the two satellites, causing some channels to work and some not. It may be working now, but chances are you have a bad mount or possibly trees in the way and the wind is causing it to come in and out. I'd setup a tech appointment to come fix it.
You can also press home three times then go down one to status then over to send status. Check connection then test signal. If you are on 119/110 satellites you want to be high 50s to low 70s depending on location and if on the 72.7/61.5 then you want to be 50-60.
Once you are under 30 you start having issues.