Adams Pro Pressure Wash Locked Up Help

[Ace0751]

I just received my replacement pro series pressure washer today and got it all connected and it was running great.  I ordered the MTM Hydro canon last year on this site for another pressure washer and when I attached it to that previous pressure washer, it locked up and was a pain to get free.  Thought maybe it was not enough pressure.  Skip forward to today and I connected the foam canon again thinking I have enough pressure now.  As soon as I tried to foam the car, the pro series pressure washer locked up and now I can't get the nozzle off cause it's under pressure.  Went ahead and drained all the water to relieve some pressure but still did not work.  I may have to unscrew the foam canon where the pipe tape is just to get it off, but wondering if there are other ways to relieve the pressure with this pro series pressure washer?  This is just my luck, should've just kept it off and washed it the 2 bucket way until I got a new foam canon.