Was the glcd ever miswired?
That can damage the Vee powersupply which means nothing will show up
as the lcd can't get its needed contrast voltage.
I did antecedently slot the LCD in offset by one pin once (20 connected in place of 19, 19 in place of 18, etc). However I was not getting any response out of the screen before an after that time.
I'm not sure what the effects of hooking it up that way might be.
Can you measure the voltage on Vee (glcd pin 18) and Vo (glcd pin 3)?
They should be negative with respect to ground.
The voltage on Vo should vary when you turn the pot.
I did measure a voltage across them. -0.25
So you are saying the voltage on both Vee and Vo is a constant -0.25
and the voltage on Vo does not vary when the pot is rotated?
Then either your wiring to the pot is bad, the pot is bad or the Vee power supply is smoked
from the earlier miswiring.
Can you post a clear closeup photo of how you have a the pot hooked up?
(I'm assuming that diags is still passing?)
What about the backlight? Do you have that wired up and is it on?
Are you using a current limiting resistor for the backlight?