Water level is the most important thing when it comes to automatic covers. The water in the pool supports the weight of the cover and reduces the strain when opening and closing it. If the water level is below the skimmers you're putting a lot of pressure on the track, ropes, and motor, which can cause the cover to not operate correctly. Just as important as the water below is the water on top of the cover. Anytime your cover is closed you should have a cover pump laying on top. If too much water collects on top of the cover it pulls the cover down once again adding strain to the track, ropes, and motor. Too much water on top of the cover or not enough underneath can both cause the cover not to open.
The cover box should also be maintained regularly. Leaves and other debris can collect inside the box and cause issues, so its important to clean them out. Not only are you adding that dirt and debris back into the pool everytime you open and close the cover, but it can also clogg up the mechanics of the cover as well causing things to malfunction. In addition to debris, make sure water isn't collecting inside the box and sumbersing the motor. If this happens the cover typically won't work until the water is pumped out and it has some time to dry.
If you ever go to open/close your cover and nothing happens there are a few things you can check before placing a service call.
1. Verify the water level is where it should be.
2. Check the main breaker and fully turn it off before turning it back on.
3. Look inside the cover box to ensure theres no water or debris getting in the way.