USB internet option for tethering greyed out. How to fix it? Under Settings → Wireless and networks, USB internet will not highlight nor will it let me activate it. Therefore, I can't connect my smartphone to the PC.
Is there an alternate way to check why this is occurring and fix it?
I wrestled with greyed-out USB tethering for 3 days.
I factory reset, changed VPN settings (when for an unknown reason I lost data capacity), read all the forums, etc.
It's embarrassing. Despite having a $40 metal-braided, multi-tipped cord with amazing mall-metal jacks that works for charging, for tethering it wouldn't. Trying the $3 cord I had the same effect, I discovered it was the cord. That's all.
The expensive cord obviously isn't made to do anything but charge, and the cheap factory cord was simply defective. (When I wiggled the wire where it goes into the hack, my phone beeped and all the charging/tethering options appeared.) 
That whole time it was the cord, poorly manufactured or damaged.
Try a brand new cord. It's likely just that. (My defective cord was only 1 day old!)