'14 Volt not able to charge on Level 2, but could charge on L1 (8 amp and 12 amp)

My '14 Volt was bought new and now has 48K. It's been charging nightly on a Blink Level 2 home charger for the past 3 years. I've also charged it at public charging stations often. It's been very reliable so far.

So this week, when I plugged in the car to the Blink charger, I expected the car to initiate a charge for 20 seconds, then stop, with the car's charging indicator to flash slowly to indicate "delayed charging."

What I got instead was the car trying to initiate a charge, stop, start again, stop--it never would get to the "delayed charging" phase. Each time it starts and stops, the car honks once. On the dash, I saw a message "Problem Detected with Charging Station," No CEL displayed, and Onstar couldn't detect any error or fault codes.

So thinking that maybe I had a problem with the Blink Charger, I tried using 2 other Level 2 chargers:

a Panasonic portable EVSE (from a '11 Leaf) that was upgraded by EVSEUpgrade to a Level 2, and,
the Clipper Creek portable EVSE (from a '16 Volt) with a 240v adapter.

Both of these chargers also exhibited the same issue--the stop, start, stop... error.

But my '14 Volt charges fine on the supplied Level 1 charger (either on 8 amp or 12 amp). No errors or problems.

And interestingly, all 3 Level 2 chargers work perfectly fine on my 2016 Volt--no errors or problems.

Any ideas why my '14 couldn't charge on Level 2? I'm going to try a public charging station next, so that way I can rule out that possibly something is wrong with my house wiring or utility.