Pictures in a bit, but I’ll bet your DFB just isn’t fully threaded in. Assuming the bearings are still flush with the outside of the shell (highly likely since you didn’t take them out and there’s a spacer between them), you just need to tighten it down.
Shift into the largest front sprocket, smallest rear sprocket, hold the rear brake, and stand on the captain’s pedal for a moment. The torque from the chain on the freewheel will thread it on the rest of the way.