New to me C2 - interesting problem

Good morning, I bought a C2 from marketplace for my son who wants to get into this hobby. Long story short, there was a benchy file saved on the C2 and it printed great! However, any other stl file I put into the C2 will not turn out. It goes through the onboard slicer, but then doesn't print properly. It appears to try and make a raft with 1 layer, then just goes to the corner of the bed and makes layer on layer on layer in the same line. somthing is goofy and I don't know where to start. I have tried several other stl files through the onboard slicer and through cura and through the Octoprint gateway. No dice. Just does that weird layering. Any recommendations on what the first steps should be? I tried to get the cura for robo working but it wouldn't work on my windows computer no matter which way I opened it.

thanks in advance. We are going to a 3d printing class in a couple of weeks, so I wanted to get him a bit familiar with how it works before we get there.

Daniel