I have an old iMac mid-2011 so I cannot install Mojave beta. I have installed the latest iOS 12 beta on my iPhones.
When i open Photos on iMac, connect my iPhone to iMac and select the device I see "No Photos" in the Photos application.
No photos from iPhone found in Photos app macOS High Sierra.
did you get an answer to this? My High Sierra is doing the same - on iOS 2t but it looks like I have not synced since end of 25