Unable to progress solo story after dropping into a co-op game

I joined a local co-op game with one of my kids today and now I’m unable to progress in the story with my character. I was a couple of planets ahead of him and now I can’t get back to any of them when playing solo. My objectives are still active, but there is no way to travel to them. I’ve already completed all of the objectives for the planets I still have access to, so I’m completely stuck.

Is this expected behavior? How do I fix it?