iPhone iOS 10 compatible with Mac OS X 10.7.5?
iOS 10 requires iTunes 12.5.1 if you're on a Mac. However, the last version of iTunes to support macOS X Lion is 12.2.2.25, so I'm guessing that's your problem.

If you still need to be able to transfer media such as photos and music between your Mac and your iPhone 6, you can opt to use third party software. One example is iExplorer which happens to still support OS X 10.7 and iTunes 10.

Another possibility, depending on your actual model of Mac, is to install newer versions of macOS via alternative methods. If you want to pursue this, please post another question providing full details of your Mac hardware (including model, RAM, etc).