Well, just on top my head, might be dumb but worth a look.
- *both rewind levers are at "off" position i assume.
- clean contacts of the prism and body, and its locked in correctly.
- if its in P - S, you need to change your aperture to the smallest (AF lens for sure, not sure how AIS works)
- if using AF lens, AF contacts clean? AF gotta be locked before it will fire on AF--S.
- One time it happened to me, blinking LED without film, will only fire at its own wish, if not it will be blinking, but solved itself after i loaded the film.