Why is scientific atlantic explorer 3250hd not working?

Surge protectors for the electronics are like Firewalls for your computer. You need to use them if you have them.Any cable guy who says, that You get better results plugging the box into the wall is full of crap. At any rate, if the issue does not clear itself within one day, or just keeps reoccurring again and again, I would schedule a service call and then request an in-house cable technician not an independent contractor. Then the In-house techs are generally more to be at knowledgeable about cable problems than the independent contractors because of the IHT's are directly connected to the cable company.
When you are trying to make the call, have them check the signal strength from both outside that is the drop pole line and even the inside the home that is wiring and if necessary replace your box with a different model.