Your antenna needs to be aimed. My antenna is mounted on a wooden post; I think the post twists as humidity changes, so I have to re-aim my antenna a couple of time each year.
This isn't hard to do. Hit the "Menu" button on your controller, then follow the menus to get to Setup. Pick "Satellite", then "View Signal Strength". It will go through the different transponders and report signal strength, which should be in the high nineties. When you hit a transponder with a low reading, pick "Signal Meters". It will stop on that transponder and give you a visual and audio indication of signal strength. Now you just have to adjust the antenna until you get the best possible reading.
It's best if you have a helper in the house to report the readings, but I've done it myself by calling my cell phone from the landline phone, and listening to the audio strength over the phone. You're trying to get the audio indicator to cheep as rapidly as possible. Adjust both azimuth and elevation, going back and forth. The adjustments may interact.
It's a good idea to mark your original position with a pencil or Sharpie before you start, as it's easy to knock the adjustment way out of whack once you loosen the locknuts.