Unable to import into Photos from iPhone over USB?
One of the fixes in OS X 10.11.2 is:


  Fixes an issue that prevented importing photos from an iPhone to a Mac using a USB cable.


Source

Use the App Store’s Updates tab to install the update. 

Why are you still on an old beta build? It's not advisable to rely on a beta operating system; it’s in a state that Apple hasn’t yet deemed as being stable enough for daily use. Even if you don’t have any problems now, you may end up having some as apps and drivers get updated. You’re also missing out on the latest security fixes.