I don't have this machine. I know some of the machines I do have, one has to turn knobs or levers in a particular order for them to work. Some knobs are turned, some are pushed or pulled. Do you have a manual for your machine or one similar to see if that might be the case? Have you oiled it? For frozen parts, Tri-flow works a little faster than just sewing machine oil. I know some of the Brother machines have a spider type assembly on the bottom side of the top, to distribute oil to various places on top. Sometimes it takes time to get things to loosen up and old oil flushed out. Some of the tops look like one needs to take something else off first, but just undoing the visible screws, the whole top lifts off. Sometimes knobs DO need to be removed first. Of the ones that I have that the knob needs to be removed, most will have a set screw on the side to undo it.
We like pictures. Good luck on getting it back into working order.
Janey - Neat people never make the exciting discoveries I do.