rebuilt tranny not engaging

[cirrusplayer]

I recently had a transmission rebuilt by a reputable mechanic. I re-intstalled the tranny with a new b&m torque converter. I did the installation myself but now the tranny will not engage any gear. this is an automatic transmission. could I have missed sometion?? vacuum, electrical. Please don't tell me i have to pull that thing out again. can any body help me??????