One of the resons for the mirror not coming down, is that the thing that was supposed to happen before the mirror drops, didn't happen. The thing that has to happen first is that the shutter has to close. It may look like it's down (rear curtain), but it may not be all the way down (I had this happen with a Program Plus). I know of two ways to un jam it. The first is to hold the camera in one hand, and smack the bottom of it into the heel of your other hand. The other way is to lift the shutter curtain (leaves) and let them drop back down. You can use a toothpick or a thin pick to lift it.
BR From: Stephanie Stiavetti ...the mirror is stuck in the up position and replacing the batteries hasn't fixed the problem. I tried to gently dislodge the mirror and it will move back to the down position, but then it pops right back up. neither the shutter release or the film advance lever are functioning.
