I have taken apart my Rexel No 87 staple gun to free the trapped staples and I cannot remember where all the pieces fit. Do you have a diagram of the inside of the gun, please?

Check you owners manual or visit the local hardware store. You may meet someone new.

try where you got it .OR
https://www.google.com/search?q=rexel+2001+staple+gun&oq=rexel+2001+staple+gun&aqs=chrome..69i57&sourceid=chrome&ie=UTF-8

try rexel for a replacement, they might do the job.

Rapesco Part number is: S14082M3. I've used these without problem

apparently Rapesco has now changed to Tacwise and they are now sold as
Tacwise 0346 (Type 140)

open and check the clip from where the pins come out for staple. may be one or two pins are stuck in it.

1. • 1 Push in the push rod plate on the back of the Arrow T50P and press down to unclip the push rod from the gun. Pull the push rod out of the staple channel and away from the staple gun.
     
   • 2 Insert a strip of staples into the channel with the tips of the staples pointing toward the bottom of the staple gun.
     
   • 3 Place the end of the push rod into the staple channel of the gun. The end of the push rod has a small, solid piece of metal that fits into the staple channel.
     
   • 4 Press the rod all the way into the staple gun until the rod plate engages in the notch at the rear of the gun.
     

call Arrow and claim defective product or buy a new one. Once you mess with the insides you need to remember the order you took the pieces apart.

Have had the same problem but now it

At the back of the staple gun is a flat shaped metal piece. It's at the bottom. Push in, pull down, then pull the mechanism out. You'll see it's a metal rod with a spring, that is attached to that flat metal piece. The spring pushes against another flat metal piece, that has a hole in it, and travels back, and forth on the rod.

The flat metal piece that the spring pushes down the rod, pushes against the staples.

Remove this spring mechanism, slide the staples down the rails. The staples will be in the position of an upside down U. Replace the spring mechanism, and lock it back into place. (Push in, pull up)

Should, your question be in reference to the fact that you have staples loaded, but upon pressing the trigger nothing comes out:

In the front of the staple gun, is a flat metal piece that pushes down on the staples. One staple at a time. The flat metal piece is shoved down by spring pressure. The spring pressure is applied to the flat metal piece each time you squeeze the trigger. (Flat metal piece = Hammer)

Sometimes, Two staples try to come out. When they do, this flat metal hammer is stuck up in the gun. To free the flat metal hammer, remove the spring mechanism out of the back of the staple gun. (The spring mechanism discussed above) Remove any staples in the gun.
Try to use a flat blade screwdriver, and see if you can shove the flat metal hammer in the front of the gun -> UP.
(DO NOT have the staple gun pointing at your face! DO NOT squeeze the trigger! DO NOT use excessive force)

If this method is of no avail for you, you have to disassemble the gun, and remove the metal hammer, and stuck staple/s.