That's ok, I know how annoying it can be to find a tiny little bug. And I suppose that's what we're dealing with here, as I somehow solved it!
First, to answer the questions:
- I did not remove the old folder, but see the next question:
- I dragged FGx from my Downloads to Applications, overwriting the entire old FGx folder
- Nope, the first time I launched it was from the Applications folder
- I did not, until a minute ago *
- I did not
- "FGxFlightGearLauncher - 2.8.0"
*I clicked the little 'folder' icon next to the "Path to FlightGear program (fgfs)" and it was correct. So I clicked 'cancel', as to make sure I would not change it to a faulty value on accident anyway. Then I did the exact same thing with the "Path to FlightGear data directory (fgdata)". Then I clicked Start and it worked! So to be clear: I opened FGx, went to the "Core Settings" tab and checked both the folders,
but clicked
Cancel and not
Choose.
I'm pretty sure it was the fgdata folder, because: after checking the fgdata path, it warned me -even though I had clicked on cancel- "Importing can take a few seconds", so I clicked "Import" and it's working again.
So maybe it would be a good idea to somehow automatically recheck the fgdata path on startup of FGx?
I hope, and I'm sure that this will help you at least a bit further
Good luck with it!