Select computer will not tween


I work at a camp and use toon boom harmony. One of our campers uses their computer, and follows the steps to make a tween, but it doesn’t work. The line doesn’t appear between the two keyframes, and it doesn’t make the tween.

I can’t figure out why; I restored the window preferences, and turned a ton of things on and off.

Anyway to get this working so the camper can tween? All the other computers, who were installed and activated the same way, does not have this issue.

Could you send a screenshot?

Then It could be easier to understand what’s going on.
You can’t add file in a comment but if you edit your first post you can add a file there.

There’s nothing to screen shot. It looks normal even after a window reset. Nothing is wrong with it at all. It’s a fresh install.