How to auto re-connect to mobile network using XBIB-CU-TH with XBee Cellular 3G?

Using XBIB-CU-TH development module with XBee Cellular 3G module. It connects to network (ATT or TMobile) via XCTU, but when battery is unplugged, and re-plugged an hour later the module does not auto re-connect to network. Seems to require a jump start via XCTU. Any way to bypass this?

Check if you’ve enabled sleep mode (ATSM), and if so, ensure that your dev board/hardware is set up appropriately to keep the XBee awake when USB is not plugged in.

The XBee Cellular module does not behave differently when XCTU is communicating with it versus when it is not, so there is something else at play.