Was doing maintenance on JD 500 today. Took the deck off to change mower blades. When I put deck back on I couldn't unlock the Mower Lift Lever or manually move the pedal. I have done the deck removal thing several times on this mower and many times on my older JD years ago. I am baffled how to fix this. Would appreciate any ideas. I did lower the spring tension to no avail. And the height adjustment is set all the way down for the deck removal and now I can't rotate the knob to a higher number.