If you've sent to printing some document and haven't found it on a printer, it may mean one of the following things:
Such situation happens rarely, but it cannot be ruled out. Someone else could by mistake take yours sheets (especially if they waited too long for pickup). It is best then to pick up printouts directly after sending them out for printing.
If you'll send for printing more pages than your available balance, none of them will be printed (do not count for printing "as much as possible"). Just check your balance and choose only amount of pages contained in that number.
Printer is just a device, and sometimes malfunctions happens. Printing is then not possible, or worse, quality of printout is very low. Most of the time it happens because of lack of toner. For students not to lose needlesly their balance, we block printing possibility until dealing with issues.
It sometimes can happen that paper jams in printer. Appropiate warning explaining an issue appears then on screen. Inform about it staff in room A1-26. Problem will be fixed, and damaged pages added back to a balance.
Never try to fix anything on your own!