The worst case possibility is a broken pump.
Are you sure you engaged the torque converter to the pump correctly before bolting the bell housing up? If the tangs weren't correctly aligned, that will ruin the pump.
X2, converter slips forwards a bit, not noticed, breaks lugs on pump when bolting transmission case to engine. Take a trans cooler line loose & fire it off, should get lots of ATF flow . Missing or broken trans filter?
Also even with out any electrical connection this transmission will have reverse & 3rd gears.
