OurWorkbench is always so good with the machines! Another good point by Juliasb, some machines require a hole in the bobbin at a certain place, you can still get it going but not quite placed correctly with the smooth side.
I've had issues with my Sidewinder loading the bobbins in a V shape, in my case that was when the batteries were low, I just did an extra direction of the thread with my finger at first -- now I replace/recharge the batteries more often. The Brother just made a loose rat's nest of tangled up handfuls of thread before it gave up and considered it full.
The same friend with the long arm had two higher end Brothers, one an embroidery machine. The bobbins looked so alike but were just very slightly different and while both fit both machines, the wrong ones did give fits to the wrong machines. Her life became better when she threw out all her old bobbins and bought new ones, marking one of the machines with permanent markers.