cannot sync with imac

This appears to be a bug in iOS 17.2.1. There are two workarounds that work for most people:

Plan A:

• Turn ON Airplane mode
• Turn OFF Bluetooth
• Try to sync again (this worked for me)

Plan B:

• Launch Activity Monitor (in the Applications/Utilities folder)
• start the sync
• In the Activity Monitor App search for MDCrashReportTool and Force-quit it. 

Some people have also reported success with disconnecting their Watch

Yes, this is only an iPhone problem, it doesn’t affect iPads. Plan A has worked for most people. When you put the phone in Airplane mode make sure Wi-Fi stays on, and turn it on if it has turned off.

Lawrence, would you please clarify to be certain I understand. As we follow Plan A, I believe turning ON Airplane Mode actually turns OFF Wi-Fi.

Use Airplane Mode on your iPhone, iPad, iPod touch, and Apple Watch - Apple Support

So if that’s right, should Plan A look like:

• Turn ON Airplane mode
• Turn ON Wi-Fi
• Turn OFF Bluetooth
• Try to sync again

Thanks for clarifying.

Correct; I left out turning on Wi-Fi, because once you have turned it on while in Airplane mode it will “remember” that setting for the future. I missed the fact that not everyone has done this.