First off, sorry if this has been covered.

My issue:
ONLY the driver side master switch will roll down the windows. all other switches don't work and are plugged in and illuminated. What am I missing?

 

 

I know that switch, Thats not the issue unfortunatly

 

Clean/Replace the master switch.

 

Its a new Delco, still same issue

 

What part number?

 

25779767

 

Check the connector wiring/contacts.

 

is there a pin out diagram of any kind? That way I can check voltage or test at all window switches?

 

Power windows are on page 88. That and more can be found here: https://schwarttzy.com/h3-hummer/

That said, I had a similar problem. Not sure where you acquired your parts, but I went through three different switch assemblies before I found one that worked for me. I can only believe that the ones that didn't work were not for a hummer.