Please help on pressure switch stuck closed

I have a nordyne/fridgidare l1ra 090c-12b furnace. When I turn the heat on the inducer kicks on followed by the igniter which then I hear a clicking noise followed by the igniter turning off and the control board giving me the pressure switch closed error. I have replaced the pressure switch and I am still having the same problem. Once in a while it will fire and heat the house but it very rarely happens? What else could it be other than the pressure switch