Mac won’t update past OS X Yosemite 10.10.5
My mac is stuck on OS X Yosemite 10.10.5 and won’t update past that, no updates on app store no nothing, I recently bought an iPhone x and iTunes won’t let me sync my old iphone back up because it needs an update which i cannot get, its frustrating me, I don’t know what to do anymore, I’ve looked everywhere on the internet and can’t find a solution. My comouter is a Mac mid 2011