Hi, I could really use some help troubleshooting this problem. I have a very lightly used  Juki 1541s. Has been a great machine up to now, but I made some standard adjustments to change the presser-foot height to handle a big stack of material. Also changed the walking feet to handle some cording. Then I went back to what I thought were standard settings and adjustments and the walking foot / presser foot combination. No idea what I did wrong, but now my presser foot bar doesn't move -