For the first time in 4 years, I got this message yesterday, "Inoperable HV Charger". At the time, I was at 29% and my other dial read around 75%. After restart, the message disappeared. In any case, I drove it to the dealer to charge up normally figuring if there was a problem, I could have them look at it. The car charged normally for the three hours I was there. Today, I am going to test again at the free charger at Whole Foods to see if charging is normal.
If the message repeats or there are other funnies, I intend to bring it into the dealer for a service visit. Hoping it was a gliche and not anything serious.
UPDATE: Good news, I charged to 100%+ today without issue at a free commercial charger at Whole Foods. So far, it would indicate a spurious message or at worst an impeding issue.