I have been having a problem getting my heated bed to heat up. I would set a temperature for it to heat up to, say, 60º C, and turn it on, start the print, and it would say "Heating Bed". However, it would remain at room temperature and the thermistor would read around 20º C. Also, while it said "Heating Bed", it would heat up the extruder instead. I thought I might have miswired it, but I checked and all wiring is correct. I also tried switching where the heated bed's wires were in the terminals. I got it to work a bit when I was getting the printer set up, but it just stopped heating pretty quickly and I couldn't get it to work anymore.