Mirror doesn't reset after shutter release?

I own a Nikon FG traditional film camera. It is only allowing me to take pictures and advance film when I'm in bulb mode. Otherwise, I can press the shutter release and then the mirror goes up, it takes the photo, but the mirror doesn't come back down. Also note that the light meter is not functional (I'm relatively new to film photography, I'm purely digital so far).

Added (1). The bulb functionality on mine is open shutter as long as you hold the button or cable release. The camera is from 1982 and it was my fathers who has long since lost the manual. The confusing thing is that it worked for me several months ago just fine. Would it be something electrical? Because I read that the shutter release and light meter are electrically controlled on this camera.

Well in bulb mode, the mirror goes up and stays up. It could be that you need to release the shutter again to lower the mirror. There are generally two ways this works, with some shutters/modes you press the shutter and as long as its held down the mirror stays up, the other way is that you press the release to pop the mirror up and again to lower it.

However, if your camera is broken and it sounds like it is, then the solution is to have the camera repaired. Luckily mechanical film camera's are the darling of many repair shops. Its the digital ones that many shops won't touch. The cost of having it repaired may cost more than replacing it.

Try a manual for the camera and see if you might be doing something wrong before moving on.

EDIT:
Have you tried changing the battery?

I'm not familiar with that camera, however I've seen an identical problem caused by the deterioration of the light seals.

Film cameras have lots of rubber based seals to ensure that light doesn't get to the film other than through the lens. This includes the posibility of light getting from the viewfinder to the film.

So I would check if the light seal which the mirror sits against when up has gone tacky and is holding the mirror up, if the mirror drops when *very lightly* touched then this is likely. You can buy kits to replace the light seals fairly cheaply - look on ebay. If you are not confident of you mechanical sympathy, then take it to a repair shop.

I'd agree that the battery is probably due for replacement.

Does it have a full manual mode and if so does it work in that?
Any Programme / aperture priority / shutter priority mode will depend on the light meter and hence the battery.