The iPhone software update server could not be contacted. An unknown error occurred (-50)

I have searched for an answer, but most pertain to syncing a device. I am getting this error on a mac when I am trying to update the itunes software from 12.4.1.6 to 12.5.1. Everything I find says to first get the latest iTunes, which is what I am trying to do.

Any suggestions?

Internet connection is working, Appstore comes up and looks for updates but does not find one for iTunes.