Unknown error (-50)when trying to sync phone

I have an iphone 6s (iOS 10.0.2). I have an iMac (27 inch, late 2012) running macOS Sierra version 10.12.

I recently updated both my phone and my mac, (not sure if that relates to my problem). Tonight when I try to sync my phone, I get a message saying that "my phone cannot be synced. An unknown error occurred (-50)."

What is this error and how do I know what to do about an unknown error? When I searched for info and what to do, it looked as if I may have to reset my phone to the original factory settings and restore it. I would rather not have to completely restore my phone (or my mac) unless I absolutely have to. Any other ideas or suggestions?

Any help would be appreciated!!