Sounds like the temperature sensor is bad. Tell support you want another unit. When you get this notice it means its cutting the charge current to save batteries. This means that even though you are wired, it won’t charge the batteries and they will eventually need to be manually charged. This warning isn’t supposed to appear until temps get down to around 0 deg.F
After a few days troubleshooting with Eufy, they decided to send me out a new doorbell.
Well the new doorbell is now installed and only time will tell how it performs.