Hey there,
I had your same problem when I first found FDroid last year; read my post about it:
Continuing the discussion from New F Droid Driver, lost and need directions:
It starts off with issues similar to yours then turns into something different but near the end I think I remember saying what solved my problem.
I also didn’t have a lot of time spare then (I still dont 
) to “debug” my phone or plug it in to get error codes, so I just kept trying until it worked, kinda like how I deal with rope "if you can’t tie a knot, tie a lot"
.