My single serve cups started to get stuck after about 2 years. Here's what I did. Picture one shows a catch on the inner base that holds the cup in place tight when blending. Picture two shows a little release lever on the back side, push down on it and twist cup at same time and it should get cup off no problem. Next to prevent from getting stuck again see picture three file/ sand the tabs as shown. I did not try this but before but you sand tabs you might try to put a little oil maybe vegetable oil at the yellow arrows in picture one.

iFixit Staff Suggestion: Visit the blender lid stuck wiki for more related fixes.