Please make sure you go through these steps:
1. Check if you have set-up Custom APN in Network > Mobile page. Custom APN can be found according to the carrier in other Knowledgebase sections.
2. Check if your firmware version is the latest.
3. Check if in Network > WAN mobile is selected as main WAN interface.
4. Check if you can ping from CLI to outside network or is it only your computer that doesn't get internet connection from RUT240.
5. Reset your router to factory defaults.