What region are you in?
If you have deleted everything on your dashboard, including the builder, you have already done what I would have suggested first.
If you have a super small app, that likely would mean that my next suggestion wouldn’t help (I’ll bet the app I would suggest is smaller, but it probably doesn’t make a difference).
One last thing to suggest is to try https://fly.io/terminal - click on “Launch Web CLI” in the lower left. See Introducing fly.io/terminal - #2 by rubys for the app I would suggest… you can copy/paste those lines directly into the terminal.