I watched the video again and think that I steered you wrong.
I agree the cam and cam follower seem to be in the wrong position for locking and unlocking the lid. It appears that the pieces that I pointed to seem to be in the correct position for when the lid is open. I can't find a free online manual.
If I had the machine in front of me, my inclination would be to raise the needle to the highest position. Then I would follow the instructions in the manual and is indicated in video to hopefully move all the parts to be in a position to open the lid. Next I would probably take the lid off and see where the metal piece that has the red line on it leads to. Maybe jiggle the knob a little and see what moves, if anything. It is possible that there may be some old oil that has glued some pieces together.
I would also be interested in what the top looks like from the inside when it is removed and what pieces go from the opening knob to the top of the machine.
Janey - Neat people never make the exciting discoveries I do.