4 Speed Shifter Not Catching Reverse

I've got my A833 on the bench with shifter and rods attached. I can shift through 1-2-3-4 normally, but I can't seem to catch the reverse lever.

I had the shifter apart to clean it up and re-grease it. At the same time I removed the bayonet receiver and swapped in a bolt on. The reverse detent spring is in place and I put it back together just as it came out.

What am I missing?

Thanks