The iPhone cannot be used because it requires a newer version of iTunes.

I am trying to sync my iPhone 6s Plus (version 9.1) to my iTunes on my PC (iTunes version 12.1.2.27) but when I plug in my iPhone to the USB port it tells me that "The iPhone cannot be used because it requires a newer version of iTunes. Go to www.itunes.comto download the latest version of iTunes." When I try to update my iTunes it says I have the latest update. Everything seems to be up to date. Why is everything with Apple so complicated?!?! I miss my android phone so much already. I just want to put MY music on MY phone...grrrr 😟

Also, both my husband & I just got the iPhone 6s Plus... we only have one laptop-- are we both able to sync our phones on our iTunes with the one laptop?

Thanks!