I have a Mac Air 2012 and can now not connect my iphone - not appearing in Finder. Asks to update software on mac but then fails (cannot connect to server). I could always connect previously.
[Re-Titled by Moderator]
MacBook Air 13″, macOS 10.13
If that Mac is still running High Sierra, update it: Update macOS on Mac - Apple Support
That may or may not fix the "cannot connect to server" problem, but I happen to know it has been an ongoing problem with High Sierra for a while.
Back up your Mac as a matter of course. To learn how to use Time Machine please read Back up your files with Time Machine on Mac - Apple Support.
If that Mac is still running High Sierra, update it: Update macOS on Mac - Apple Support
That may or may not fix the "cannot connect to server" problem, but I happen to know it has been an ongoing problem with High Sierra for a while.
Back up your Mac as a matter of course. To learn how to use Time Machine please read Back up your files with Time Machine on Mac - Apple Support.
I think the bug "cannot connect to server" happens because High Sierra is already a very old software and I think that Apple has already shut down the servers for the High Sierra Mac App Store, which means that you need to download the software installer from another source (which may be insecure, if you are not downloading it from a "safe"/"trustable" source, like the Mac App Store). On a more recent Mac (Intel based Mac), you could download, for example, the macOS Catalina installer from the App Store (Catalina 10.15) and, after that, on that Mac, you could create a bootable drive with it (How to create a bootable installer for macOS); macOS Catalina is natively compatible with the 2012 MacBook Air, however, if you find it a little heavier, you can try Mojave (Mojave 10.14).
Unable to connect iPhone to MacBook Air
