Usually the problem with just about every 1100 and 11-87 that comes into my shop is either the shell latch tip is broken {Remington had a bad run of these} or the action tube has gotten water in it and rusted so bad that the action spring and plunger cannot move properly to allow the action to function. The shell latch wont make the gun not open, it will just fail to feed properly and jam. The action tube issue will certainly make it not open and the give away to this is typically that the bolt feels really rough when you are moving it.
If it is the action tube rusted you will need to remove the stock. Remington used a slotted nut that comes off with a large straight slot screw driver {if it comes off at all, you might have to soak it and sacrifice the stock to save the action tube.} Be careful, if you mess up the action tube it has to be brazed into the receiver and that means a refinish. Remington has an upgraded nut that is a hex and is driven by a socket.
There is of course a lot of other things it could be and without having the gun in my hands....well, too bad we are a country apart. Otherwise ask away or give me a call, I might be able to talk you through it.