I own two laptops. The smaller one is a jh something or another from asus with win8.1 installed. I plug in my iphone 6+ via usb and she tethers instantly just fine. My larger laptop is an asus 750, also win8.1 I plug my 6+ into this laptop and tethering does not engage. On the network popup menu my phone is available via wifi but not for tethering. Also noticed, when the phone is usb connected,its not listed under devices in the file manager. This laptop tethered just fine with my iphone 5. -scratches head- Anyone know whats going on here?
Have you checked iTunes is the latest version it would need to be the latest version so it installs drivers that recognise the iPhone 6
It might be your iPhone or your laptop. My 5C also fails to be detected by my new Dell Windows 8.1 laptop even though it can share its internet wirelessly with my other devices.