Settings > Network > SIM cards > Check if SIM 2 is active.
Below that, select SIM 2 for Mobile Data.
Settings > Network > Mobile Network > SIM 2 > Roaming , Allow to connect to data services when roaming.
thanks for answering. it appears that i had to deactivate sim 1 to allow sim 2 to have data. since i dont have a phone number at sim 1 i dont really care but i don't think that a dual sim phone should work that way...
I really didn't understand you.
If you are using only 1 SIM, Use it in SIM 1 Slot as it can connect to 4G LTE.
IF You are using 2 SIM cards simultaneously, Settings > Network > SIM card > Preferred SIM for > Mobile Data,
This setting should work. Also check the Roaming option in Settings > Network > Mobile Network > SIM 2 > Roaming