On step 4 of the tutorial it asks you to go to a system and select an asteroid belt.
I go to a system and select a belt for it to tell me someone is already occupying this system. Makes sense other than the fact that every system has been empty that I've visited, and I've been to 5-6 different empty systems to receive the same issue, can't progress further in the tutorial.
As a note, I can still make accretions, so it doesn't really impact gameplay, just the tutorial (unless there is something drastic that I'm missing).
EDIT: I think this may have been an issue on my part. While I was typing this one of those systems which appeared empty suddenly has planets. Maybe they were loading?