The "could not activate cellular data network" error means your iPhone won't be able to use the mobile data you're paying for ...
Lifewire on MSN
Fix 'No service' on iPhone with these checks
Make sure your iPhone isn't on Airplane Mode because it turns off cellular and Wi-Fi services. Restarting your iPhone can ...
Common causes include carrier outages, outdated carrier settings, corrupted network configuration, and SIM/eSIM provisioning errors.
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