In off-line mode, airgradient in perpetual reboot cycle

I have an airgradient, one, I-9PSL. After a bit of trial and error I managed to update the firmware from 3.1.1 to 3.1.9.
I have been unable to connect it via WiFi (subject of a different post). So, I set the monitor up in off-line mode.
However, in off-line mode, the monitor enters an ongoing reboot cycle. It boots up, shows various outputs from the sensors and does this for about three minutes. Then it shuts down and begins to reboot, repeating the cycle, endlessly.
I would be grateful for any thought on how I might fix this.