The cellular interface of a Digi TransPort is not obtaining a certain expected static mobile IP address.
Because the TransPort uses the mobile IP address that's handed to it from the cellular provider, this is a provider issue and not a Digi issue.
Contact the mobile provider to ensure the account/plan in question is setup properly on their end, to provide a static mobile IP address. Typically, the type of plan that offers a static IP is a "Mobile Terminated" plan (NOT a "Mobile Originated" plan). If using a SIM card, ask the provider what APN should be used, and adjust the APN value within the TransPort's configuration as needed, to see if that helps.
Related KB articles and documentation:
Verizon 4G LTE Static IP APNs
Mobile provider APN list
Mar 21, 2019