welcome to Digi Forum. Unfortunately there is not enough details in your question to be able to proper help on this issue. The reasons for cellular connection not working can be several (APN not set correctly, old firmware, no coverage, misconfigurations, hardware failure, etc).
I would suggest you to please send us an email to Tech.Support@digi.com with IMEI of the device and a debug.txt file (https://www.digi.com/support/knowledge-base/how-to-extract-the-debug-txt-file-from-a-digi-tran) so we can open a case to further assist.
Please also review Digi Support Level options here: https://www.digi.com/support
Digi Technical Support Team