[88Silver924S]

You say all the window switches are new. Are they Uro brand perchance, a brand infamous for failure (including failure at launch/when new)? First try swapping them around to try to nail down if one switch is bad. Second, if you still have the old switches check out the excellent Clark's Garage write-up on how to refurbish them in your spare time, and after cleaning the burnt contacts and gentle re-arching of the "V" contact pieces, swap them in to see if one of your new switches was DOA.

Also testing the ground wires with a voltmeter may yield a "good" ground because the current is so low when testing but a high current draw such as a window motor will choke the system, it won't work. However since your other switches operate the windows fine that indicates that the grounds are adequate.

About every 7-8 years I have to take apart a window switch and file the contacts with a points file or fingernail emery board etc. reassemble and get back on the road. Good luck & have fun.