I have a 2 year old pool with an AquaComfort electric heat pump. The heater was working fine last year, but I have not used it at all this year. I tried to turn it on yesterday and I am getting a low pressure error. This year, I decided to open the pool (and maybe close it) myself. I had the pool company close it last year and I thought it was pretty straight forward. Could I have missed something that they did to winterize the heater last year that might be causing this error? Any other ideas before I call the repairman?