The symptom indicate that there is no voltage coming from the photocell. Of course that could be the photocell or something that obstruct the light but more likely it's FRE resistor for film speed setting and/or the aperture coupling resistor is broken. AI tab in or out doesn't matter much in fact it should show a lot of light even when the lens is stopped down. In your case the meter shows that there is no light.
I think you have to return it as it's not a minor repair unless you want to shoot only in manual and meterless. By the way, in manual mode although it works fine but the meter should show a - minus sign all the time.