BACKWIND SPRING and COVER INSTALL
Note the orientation of the small copper backwind roller spring. It's located on the very bottom end of the cover (as installed). On the other end is the film tension roller. Note its orientation. I suggest a small, hand drawn diagram if you are not sure of how the orientation of these two parts are installed. Install with the film pressure plate removed. Before attempting to install, push the lever (in the center of the cover) towards the gate (lens) of the camera (as installed). This will place the index pin of the pressure plate release in the correct position and make installation possible.
Insert with copper spring end (left side) first. Then center to mounting screw hole, while holding the film tension roller between right thumb and forefinger. I can do it first time usually, but anybody not familiar (no experience) will usually loose (fall off the cover) either or both the small copper backwind roller spring and the film tension roller. Then they won't know which way to install, etc. A diagram really helps. It’s a 3 step process:
1) install small copper backwind roller spring
2) center screw over hole
3) install film tension roller and move end of same into small hole in top plate. The cover supports one end, the hole in the cover plate supports the other.
When the cover is in place, the backwind spring will engage the backwind roller 'teeth", and the bottom end (tip) of the film tension roller will be in it corresponding hole. Some cameras have a plastic spacer on the tip. You can use a very small amount of grease to hold the spacer in place.
Now insert lid latch button and screw. The lid latch button sometimes has a 'lip', so there is an "upper and a lower" side. This lip compensates for the door closing clearance. It is not found on every camera. If the door will not lock or is loose, remove the screw and flip the button upside down. If this doesn't help, the problem is usually with the cover not being centered. You can actually 'feel' a click when the cover pops into place. Don't force anything.
Check that the small copper backwind roller spring does indeed work by trying to roll the bottom roller back and forth. It should go only one direction, indicating the spring is doing its job. Check the film tension roller. You should be able to push it towards the front of the camera and it should pop back on its own. If not, the spring supplying tension has slipped. Remove the cover, reset the spring (use diagram now!) and start over.