Shuuer stuck down, lever wont advance

Here is a link to an online manual, it appears that you may can download it. I hope this helps you.

You may download a copy of the AE-1 manual here.
If you have an AE-1 Program, you may download its manual here.

Have you rewound the film? If you rewind the file completely and pull out the rewind know, it will pop the back open . . . and can remove the film cassette. While the back is still open, complete the cycle on the winding crank. The winding crank should return to "Normal" arter you complete the winding cycle. When you close the back, everything should go back to normal.

Unfortunately film advance jams like this usually involve disassembling the camera, something only camera stores will be capable of doing.

This is a very common fault now on almost all AE1's and related models like the AV1.

Most of the time, it's due simply to age and dried out lubricants. The cameras need a strip down, thorough clean, and reassembly using fresh lubricants (known as a CLA service). It's wise during this process to remove and replace all light seals and mirror buffers as they'll have turned into a corrosive sticky black goo by now. The job is for professionals only due to the need for special tools and skills and the need to readjust the shutter speeds upon reassembly. Although it's not cheap (£80-£100 parts in the UK, cheaper in the USA and much cheaper in some Far Eastern countries such as Malaysia. If broken parts need replacing there is an extra charge), it's far cheaper than any new camera of the same quality and will ensure that the camera gives many more years of service. A freshly CLA'd camera has a resale value, a broken AE1 is usually completely worthless.

The film is either at the end or stuck. The shutter will not release unless the film advance lever has gone all the way and back.
Make a note of the frame counter. Rewind the film and remove it from the camera (When you feel the film to come loose from the receiving spool, stop rewinding to prevent the end of the film to disappear inside the can. This way you can reload it if it was stuck in the middle.) If the film was completely exposed, take it to be developed.
With the empty camera, try to advance the lever and release the shutter. If this works, the problem was the film and not the camera. Everything is fine. If the problem persists, take it to be repaired.
If the film was stuck in the middle, load it again into the camera. With the lense cap on (preferably in a dark room or similar) 'shoot' as many 'empty' frames as you had on the counter plus two more. Finish the film and develop the pictures.
If the film stucks again at the same place, rewind it and develop normally. It was a bad film.
Hope this helped you to solve the problem.

It could be a simple issue with the shutter magnets, or something more severe with the electronics. What does the meter needle do when you push the shutter release down? With the speed dial set at 1/125 or higher and no lens, the needle should move fairly high. If it pegs to the bottom right away, that is a bad sign.

You can check the magnets from the bottom with the cover removed. (2 screws) You can release the mechanicals of the shutter by pushing the silver lever arm (located next to the plastic shield around the magnet on the rewind side of the camera) toward the front of the camera. Be mindful of the spring attached

On the very bottom inside the plate there are many cog gears with levers and retractor springs. One may had come off causing your problem

The magnets that control the shutter are the likely suspect. Dirt and debris can cause them not to hold properly. Hence, it fires the shutter when you advance the film. It is something you can repair yourself. I can describe the procedure if you are interested.