MacOS High Sierra To iOS 13 Sync Problem - Updating MacOS not an option

Hi MacOSHighSierraToiOS13,

Welcome to the Apple Support Communities!

We understand that you're unable to sync your iPhone and your Mac. Have you connected your iPhone to your Mac to sync successfully before?

When you see the alert asking you if you'd like to allow this computer to access the information on your iPhone, are you able to choose "Allow"?

This is also a great resource to help you to troubleshoot your iPhone and Mac connection: If you see an error in Finder or iTunes on your computer

Are you able to connect your iPhone and sync with your Mac in a new user account? To create a new user account, you can go to the Apple menu  > System Preferences, then click Users & Groups.

Click the lock icon, then enter an administrator name and password.

Click the add button (+) below the list of users.

Complete the fields shown for an Administrator account, then click Create Account (or OK).

Once you’ve created the new account, go to the Apple menu  > Log Out, then log in with the new account and connect your iPhone again.

Let us know if this helps.

Cheers!

See About the 'Trust This Computer' alert on your iPhone, iPad, or iPod touch - Apple Support and reset your trust settings.

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