It's happened to all of us. We load a file and find that we can't move some pieces separately from others. It's like they are grouped together!
Sometimes they are grouped in the original file while other times the Glowforge website grouped several pieces together on its own that weren't grouped before.
At the time of this recording, Glowforge has an "ungroup" feature that is only available to Premium subscribers that they say will roll out to everyone else at some point. All you do is select the item you want to ungroup and right click and choose "ungroup."
It works just as you would expect it to! If that doesn't work for you, watch for other Glowforge 101 classes soon because I'll show you other ways to accomplish the same thing.