Recently overhauled transmission with new torque converter. Fluid level ok. When shifting through all gears, transmission does nothing. Could this be an electrical problem?

What year/engine?

Engine - 3800 V6 series II, Transmission 4T65E
1998 Park Ave

Overhauled as in rebuilt? The first thing that I thought of was insufficient fluid, but you say the level is "OK". Have you checked the shift linkage from the cable to the linkage (located at the park/nuetral switch)? There's not a whole lot holding 'em on and it could have popped off from previously not being attached fully.

If it was recently completely rebuilt, then I'd say someone didn't put it back together right. 4t65's are pretty complicated to rebuild. Have any kind of warranty from the rebuilder?

New neutral safety switch installed and linkage is connected. I can shift through all gears but the transmission does nothing.

Does the pump build pressure? You can at least take one of the cooler lines loose and see if fluid is circulating.