@Hubert Mirosławski , Based on my research, I find there's an iOS Device restriction policy named "Block use of cellular data" under wireless. When we select "All managed apps", then all the managed apps can't use cellular data.
https://learn.microsoft.com/en-us/mem/intune/configuration/device-restrictions-ios#wireless
Please check if we have this policy set. If yes, remove it to see if it works.
Hope it can help.
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