ZTE ZMAX won't connect when coming in from non-coverage area

I recently bought a ZTE ZMAX for use at our new home, which is outside TMO coverage.

The phone:

• Works fine when in TMO coverage
• Works fine when using over WiFi at home. 

However, when I drive to work and re-enter the TMO coverage area, it will not connect.  It keeps displaying the sad 4 bars with an x through it.

Not until I reboot the phone will it connnect to TMO.

I have tried turning off WiFi when leaving home, keeping it on, turning data off and on, airplane mode off and on, nothing works except a reboot.