Joe,
I was finally able to access my machine. It is like yours, but has a table extension. I converted to a handcrank. It toi has a cotter pin. The feed dog knob works just fine.
It has a cotter pin connecting parts of the drop feed mechanism. If the knob is not working, you can move the mechanism parts underneath to get it going.
I have pictures, but they are too big. I am on a Samsung tablet and having problem finding method to reduce picture size.