A few reports say that multiplayer games freeze before they are completed.
Unfortunately, your description is a tad vague. First, look if your XPs have exceeded the "Next Level" XPs. If so, the level stucks and you'd have to continue till the next level.
Otherwise, try to follow the XP development (in the green bar next to "Level")
and the precise happenings at game finalisation.
XPs should rise by one with each of your shots, shown by flashes of the bar, and when the final XP summations are shown, the completion points should be added.
It may be necessary to click your way to the main game screen!
Next thing to observe is, the levels get more XPs in between, around 1,800 at your level. Thus, it will take a few games (or days) to the next level.