It could be as simple as the set screw in the lifting collar has came loose. If you open the end piece and raise the lever in the back up and down you should be able to see if the collar is loose. It will be on the pressure bar and it is the piece the lever pushes on to lift the foot. If just loose you have to put it to where it needs to be on pressure bar to lift it high enough and tighten the set screw.
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It could be as simple as the set screw in the lifting collar has came loose. If you open the end piece and raise the lever in the back up and down you should be able to see if the collar is loose. It will be on the pressure bar and it is the piece the lever pushes on to lift the foot. If just loose you have to put it to where it needs to be on pressure bar to lift it high enough and tighten the set screw.