The gear ratios on that hub are-
1- 3/4
2- 1 (direct)
3- 4/3

IF you can get 2nd gear, but none of the others, the gears are probably busted internally.
But don't give up yet.
Adjust the shifting so that you are in direct drive or 2nd gear.
"Tweak" the linkage so that it's "centered" in that gear. IOW, turn the adjuster one way until it starts to skip under LIGHT pressure. Turn the opposite direction until it skips again. SPLIT THE DIFFERENCE.

IF you can get the hub to work without skipping in either 1st or 3rd, it's probably NOT broken, and can be adjusted.

IF you can only get it "solid" in 2nd, you can (probably) set it up to be a single speed.
The way I did it on the broken 333 I had was I took a nail to use as an "indicator rod" (the internal shift rod) I placed a small nut over the head and then screwed the cap thing with the lever on it.
I had to play around a bit to get the right length nail.
I figured 1 speed was better than none.