N900P Sprint - No data connection on abroad networks

I got this device and all works fine except the fact that with even the correct APN settings no data is being turned on when triggered. What is the trick to be able to use this? The same problem has my sister on a Glaxy S4 Sprint . If I find the solution for my Note 3 I hope to get the workaround for the other phone as well.
Im on PVPUEOK2 official build.

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