The message is advisory, not a warning of something wrong. The batteries charge state is accessed and if there is not enough charge the ESS is turned off to allow the battery's to charge up. Cause while you use the ESS it drains the battery's while the engine is off.
The WK2 has smart charging, its using computers to access the battery's state of charge and adjusting charging voltage accordingly, to charge the battery as quickly as possible but not to overcharge it, which greatly decreases the battery's life, especially AGM battery's. I.E. the charging voltage goes up and down according the battery state. 14.3 Volts sounds normal, especially in cool or cold weather.
In the past, there was a battery temp sensor, and charging system voltage was varied according to the battery temp to prevent overcharging the battery. You would see the system voltage change with temperature, going up the colder it was. Now, you will see the voltage change several times in a minute or not at all for hours. All depends on the charge state of the battery.
If you drove 45 minutes non-stop on a highway, that should have fully charged the battery. Did you get the message after that trip? If so, then I would suspect you might have a battery problem, one of the two batteries, you have a small auxiliary to be used for use when the engine is off while at a stop. If you got it before the trip and it hasn't come back, it might be perfectly normal.
Yes, since FIAT took over, there has been a shortage of parts, it was far worse at first then it is now. FCA burned many bridges with customers when they left customers vehicles sitting in Dealer lots waiting up to 6 months for parts to repair them.