Default Reverse Tethering Help

I've been trying to get the USB Tunnel/ Reverse Tethering to work for a good while now.

Cant link guide.. Let me fetch the title

So far I've gotten to the part where it says "Waiting for SuperUser Permission - 25" but I've never gotten a prompt in Superuser.

I've tried with my S3 and SHIELD Tablet, so far no luck.

I've tried SuperSu as well.

Both devices have been rooted of course.
Let me know if you need more information.