I had this in a test. I wrote the first one, "has been running" and got it wrong and the teacher wrote the second one, "has been run". I want to understand who's correct and why.
Since 1973, the festival has been running every year.
Since 1973, the festival has been run by the town's entertainment committee.
Both fragments that you wrote are incomplete, but not incorrect, and they can be completed in different ways. In "has been run", "run" is a passive form: (Active) The town's entertainment committee runs the festival. (Passive) The festival is run by the town's entertainment committee.
Unless you have been told what to express with your sentence, your answer is not wrong, and your teacher's answer is different, but no better.