Last weekend I had the same alert every time I started the truck. Took it in yesterday and the Ford service guy said they checked the battery under the hood and the one behind the back seat (2023 F150 XLT Powerboost). The backseat one was fine. The one under the hood they charged it for 2 hours til it tested good. He said something about batteries sitting to long before truck deliveries.
I told him during the winter I would put it on a charger whenever I got a "System off to save battery" alert. He said I shouldn't have to do that anymore.
Also, I couldn't get a printout of what they did because their computer system is still down. He said he'd email me it when it's back online.