It makes sense we'd lose the robot code after the reformat. That would also remove the startup executable.
When you tried to build and run as startup, did you get any errors or did both say they happened successfully?
If you try to hit the run arrow on your Robot Main vi, will this run without any warnings? (I'd expect you to get a warning about code already running if the prior steps didn't have any errors). If it does start running, do you see robot code on the Driver Station (I'd expect you would although this isn't a suitable solution as you can't use it on the field)