Hey, I just picked up a Hasselblad CF 50mm f/4 FLE.
I moved the manual/auto aperture lever to the manual position and I can't get it to return back to its auto position. Not something that I've had a problem with on my other lens. Something is jammed and I cannot press it in to move it back.
Can you try to press on the lower part of the switch (seen from above, in a normal usage condition, i.e. you looking "above" the camera).
This should unlock it, then try to slide it up.
If it does not work, can you return the lens? something might be wrong with it...
Alternately, take off the film back and fire the lens. That should clear it, but post #2 and #3 are the way to go. We all have this problem every once in a while.