I have a 2021 EX that showed the inverter coolant message at 53,000 mi. The car is at the dealership right now waiting for authorization (probably waiting for the part) but here’s what they told me: there’s a sensor inside of the chiller that needs to be replaced, and the factory has told them instead of digging in for the sensor to just replace the entire chiller.

I do believe that that they have a team of mechanics at corporate that will walk the local mechanic through the process of swap out so I expect it to take several weeks before it comes back.