If you have it apart this far I would verify the regulator valve is free and not stuck out, and check the tc valve.
If the clutches and bands pass air pressure test (use 30psi) then likely you didn’t have enough fluid or the vb is your culprit.

A stuck tc valve won’t allow the converter to fill and you won’t have cooler flow.

You should have stuck a gauge on it before you yanked it. You need converter charge and line pressure.