It is difficult to diagnose over the Internet! Perhaps you can see what is going on if you remove the fore-arm wood?? For a No. 1 Mark III* Lee Enfield, is important to remove the forearm before the butt stock - there will be a big stock bolt - the head is accessible via the butt trap - you will need a sizeable screw driver - like lug wrench size - to reach in and undo the stock bolt - the nose of that bolt will be square, it usually protrudes through the wrist and will fit into a slot on a metal plate on rear of the forearm - if you try to forcibly turn it with the fore-arm in place, chances are good you would break the rear of the forearm. Typically undo that "king screw" in front of the magazine well and the small cross screw at the rear of the trigger guard - depending on what is left on that rifle, there may be another screw forward of that, that holds a spring loaded barrel band - then remove the fore-arm keeping it parallel with the barrel - you DO NOT want to "hinge" it by pulling down the front end - that will likely break or compress the "draws" in the upper rear of the stock.
Chances are good that the trigger will be hinged to the trigger guard - and then the trigger sear arm is hinged likely to the receiver - you might have to reassemble the metal parts, without the wood, and then watch and see what happens as you are or are not able to open the bolt with the firing pin / cocking piece forward. The ones that I have "fixed" are incredibly smooth operating bolt rifles - about total wrong to not be able to open a bolt from the fired position. You could have broken pieces inside - I really have no clue what precisely is wrong with your rifle, but there are likely many possibilities.