iOS 12.1 and Photos - iPhone not "seen"
I updated my iPhone 7 to iOS12.1 on the weekend and tried to download pictures/videos to Photos on either of my old macs running El Capitan (10.11.6). Initially, the phone was identified and reluctantly the files started to transfer but then stopped - possibly because the sleep function kicked in after 1 hour.
Now, the phone is not identified on either mac and there are several items I would like to transfer. I have added a screen shot of the Photos version for information.
Is there a "switch" somewhere that I can reset - say a plist file or similar? I sure hope that the upgrade to iOS12.1 does not mean that I have to replace two, otherwise fully-capable, machines!
Any suggestions greatly appreciated.