This error message means the cellular modem module ("radio") is not being recognized by the Digi device's Operating System.
It is unfortunately very unlikely to recover from this type of issue in the field, as this is likely a hardware-related issue. However, in the chance the modem module physically lost good contact to the unit's circuit board, "re-seating" the module could potentially resolve an issue like this. PLEASE NOTE
however that opening the chassis (to potentially re-seat the module) may void the unit's warranty, so proceed with caution and consider getting specific instructions from Digi Technical Support to try this, beforehand.
Please contact Digi Technical Support and reference this KB article to request an RMA to have the unit repaired, depending on the device's warranty status.
Mar 21, 2019