What did I do wrong? FIXED IT!!

Since reverse works, it uses the L/R band and the hi-drum so those are working. That means the pump is working. And that means the TC is working, and so at least two cast slip rings are working.
No forward gears could mean the forward clutch is not working, and/or the L/R band in manual low, and/or the rear sprag. But we already know that the L/R band is OK (cuz reverse works) and if the sprag goes, you get no locomotion period.
So the bottom line is that the forward clutch is not working.
If neutral works, with no tendency to creep, then I have to agree with ikopaska, that one seal ring got snagged.
If it was me I would do a hydraulic pressure test, and if the pressure test fails then down comes the tranny.