Pentax mirror stuck

This camera can be notorious for these types of film advance issues. The bad news is that a ZX-7 is probably not repairable. Good news is that there are many used Pentax bodies out there that will work with you lenses.

is the mirror stuck up? Lots of these ZX Pentax models have failure of the mirror motors when the plastic gear on the shaft of the motor cracks and then the motor just runs continously

I just checked my SF-1, and the mirror will go through four cycles while trying to load the film. You should be able to hear the mirror go up and down when you open the back and close it, then turn the camera on. I cannot get my SF-1 to keep the mirror up. Check to see if you have the mode set to bulb, and that the shutter release isn't stuck down - that will keep the mirror up until you release the shutter button or turn the camera off.

Also look carefully inside the lens mount on the side nearest the red dot. at the horizontal spot there is an internal button. It should be at the bottom of the track it runs in, about 1/3 of the way from the screw below the red dot to the lens release button. That moves up when the mirror goes up, and down when it comes down. If it is in the up position, you could perhaps try to gently move it downwards. It definitely moves up and down with the mirror on my SF-1.

Unless you have experience repairing cameras, this is not a DIY fix. Take your camera to a reputable camera shop and have a trained professional look at it.

The problem with the mirror is 1 of 3 things, 1 mirror box is distorted from being dropped, 2 mirror motor striped teeth or burnt out, 3 batteries. Try fresh good quality batteries first, that fixes lots of problems in cameras. if its the mirror box or motor then its time to go camera shopping.
This camera came out in 1997 so is an old model. It was brought out as a very basic model, no frills. 1 hour of a camera tech's time is worth double what the camera is worth so dont even bother getting it repaired.

Your second curtain is not releasing the mirror to come down.
This happens with weak 2nd shutter curtain tension.
If the wind lever is stuck and the mirror does not come down then the mirror tension spring came off.

Mirror lockup often occurs if the batteries are flat.

Try new batteries first and if the problem remains please report back for further options.

mirror locked up? if so, the shutter curtain may not have traveled fully. gently push the curtain to the left until the mirror returns.
or the locking mechanism in the mirror box is not working. if so the camera must be disassembled to remove the mirror box for repair.
in either case the camera should be repaired and adjusted by a camera repair person. there are no new parts for this model Pentax so the repair could be expensive. get an estimate first.
i am assuming the lens cap is off.

Slr mirror is stuck. remove the lens and try to slightly move the mirror up and down ( but not forcing it to move!)and pushing the shutter switch. Try also applying lighter fluid in the mechanism while operating or shooting, fluid will help loosen the stucked mechanism.

This is a result of the linkage from the shutter release button being out of adjustment. It is a mechanical fault that can be repaired very easily.