Eureka altima bagless
I experienced the same problem of being unable to remove the dust cup. Inspection of the dust cup appeared to indicated two tabs on the bottom of the dust cup preventing it from sliding straight out as illustrated in the instructions. However, after much fiddling, I assumed that the dust cup with the tabs was probably a slightly different part than actually intended for that particular model (2996avr) and so decided to force the cup out, reasoning that if the tabs broke in the process, that was necessary for removal of the cup anyway, and therefore not detrimental.
HOWEVER, upon forcing the cup out, the cup broke away from a plate upon which it is designed to sit. The cup had apparently become stuck to the plate after much use without sufficient care and cleaning. The plate is what the tabs are attached to, and so by breaking the cup free of the plate, the tabs were not an issue, and the cup easily slid in and out of the housing, as intended. It was also observed, upon removal of the cup, that there is a very slight lip on the front of the plate to secure the cup in the proper position; this would likely act as an additional hinderance if the cup was also stuck to the plate by old cemented grime.