Why does Rhino say that it is expired? (Rhino for Mac)

Summary: Rhino for Mac reports that it is expired for various reasons.

Problem

A wide variety of problems can cause Rhino for Mac to report it has expired.

Answer

You have more than one copy of Rhino installed, and it is still starting the expired version. You must remove all copies of Rhino.

Double click any 3DM file. If the file opens in Rhino, then you still have a copy of Rhino installed somewhere.