No shifting at all?
Fluid level?
Is gear selector adjusted correctly, not hanging between gears, etc?
TV cable is hooked to trans, moves freely, and is adjusted right? ( i know you said that like 3 times...but never overlook the obvious!)

Rear seal is idiot simple, so on the front - did you get the converter seated all the way in? (three 'clicks' or what have you as it goes onto the splined input shaft(s))?
If all this seems to be 100%, then on to the filter... been a while since i've had a trans pan off, but i have had things fall out...and many trans have notes regarding 'gotchas' on filter replacement - you gotta be 110% sure you did that right! No falling BB's, to double gasketing or non-gasketing, etc.

I would suspect the filter is at fault, or the install of it...there is a pressure tap on the trans to check pressure - i can get the specs if you need it and have a guage - if the filter is blocking a passage, no or low pressure will make shifting, umm, odd to say the least.