Good news and bad news.
When I ordered the extension from EVES it said something like 1-2 weeks "back order". It gave the impression that they were made to order.
I waited 3 weeks and called them. They said they are on "back order" won't arrive until mid august. But there are newer designed ones due at the end of August. So I canceled the order (which they were very expedient at).
So I went with Plan B. I bought the Lectron 20ft 40A J1772 extension from Amazon Prime for $159.00.
I had the Lectron Tesla to J1772 adapter already and was very happy with it (very well made and has worked flawlessly).
The extension was made just like the adapter. Extremely well put together and the cable feels a lot like the 80A cord on the Gen 2 Wall Connector.
Plug it all in and nuttin. It also failed to work using just the Tesla to J1772 and the Tesla J1772 adapter (no extension).
Then for grins I tried it on the UMC and it worked. I only had the 120V 15A pig tail. So was it working at lower current (15A), Level 1 (120V) or did UMC talk differently? So I dig around the internet and I stumbled into a thread I started a while back when I was looking for the Tesla to J1772 adapter.
Charge Compatibility with a Volt (post 31 by
@CCIE )
Bingo !!! It's working perfect now and starts charging instantly.
One tiny annoyance is, there is no button to open the charge door. Every connection is locked, and safety triggers enabled (if you push the button on any latch, charging stops immediately). I'm so glad I bought the Gen 2 Wall Connector (New off Ebay long after Gen 3 was available). I suspect the Gen3 might not have that legacy dip switch. I also could not do what I wanted without the 24ft lead, I'm using every inch to get just inside the garage (no connection is exposed to the elements). Then the extension from there to the car.
So in summary you need this (I bought these both on Amazon).
Lectron - Tesla to J1772 Adapter, Max 40A & 250V - For Tesla High Powered Connector, Destination Charger (White)
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Lectron 20ft/6m J1772 Extension Cable Compatible with All J1772 EV Chargers - Flexible Charging for Your Vehichles
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Tesla J1772 to Tesla adapter that came with the car.
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Tesla Gen 2 wall connector in Legacy mode (UMC also works)
I can also charge my wife's Volt when we take her car, which is rare.
Note: This is for temporary use. Eventually I will have the Wall Connector moved to the garage.