The information on the iPhone [device name] is synced with another user account.

Dear Brian_P7,

Thank you for your suggestions.

I updated the Mac to macOS 11.5.1 and the iPhone to 14.7.1.

I still encountered the

"iPhone [device name] is synced with another user account" message.

When I booted the Mac in safe mode the iPhone did not appear in

the Finder sidebar. To address that I read the article:

If your computer doesn't recognize your iPhone, iPad, or iPod - Apple Support

I think I followed those instructions properly...

Boot Mac in safe mode (saw safe mode notation on login screen).

No other USB devices connected.

In Finder Preferences > Sidebar > "CDs, DVDs and iOS Devices" is checked.

iPhone is unlocked and on home screen.

Connect iPhone with USB cable to Mac.

iPhone does not appear in Finder, but does appear in System Information

USB Device Tree.

Restarted iPhone and tried connecting again. Still not recognized.

Restart Mac in normal mode. iPhone is recognized.

I'll try your other suggestion, creating a new user, in the next few days.

I'm also thinking in might useful to see what happens if I temporarily

set the iPhone and Mac to sync calendars and contacts via iCloud.

Thanks again.

Dear bailier,

Thank you for your help. I read through the articles that you

suggested. First, in the "See and remove your devices that are

associated with Apple ID purchases." I did indeed see that the

iPhone and Mac are logged into the same Apple ID.

In the two articles that concern "Set up iCloud" I confirmed that

the devices are logged in and that they are coordinated in terms

of which apps use iCloud and which do not. Both devices do not use

iCloud for either contacts or calendars.

In the article "Use the Finder to sync your iPhone, iPad, or iPod

with your computer." I saw that I am following the recommended

procedure to sync contacts and calendars. That article referenced

Find an iTunes or the Finder error code - Apple Support, but the

information there only concerned specific numeric error codes.

It seems the crux of the issue in my case is why does the error

message "The information on the iPhone [device name] is synced with

another user account." persist when as far as I can see all the

indications are that the devices are logged into the same account.

And why does the error persist even after both Merge and Replace

have been completed.

Unfortunately, I'm afraid the problem I'm having

is due to some idiosyncrasy on my devices because as far as I can

see there are very few users asking about this "synced with another

user account" message.

Again, thank you for taking the time to offer advice.

Dear jdo_apple,

Buried in my original long message I mentioned that the problem also occurs on

another iPhone and my iPads. It's when you select sync for contacts and calendars,

and click Apply that the puzzling message comes up.

I created a new user account "test-user" on the Mac.

I logged into test-user. When I logged into my Apple-ID

it asked for the password for the test-user account which I entered.

It then said:

Enter the password you use to unlock iMac

Access to your account is protected by the password you previously used to

unlock this iMac.

I thought this was not clear, so I tried entering the password for test-user.

It then said:

Enter Password for Other iMac

Enter the password for [my-iMac-name] which is not

the password for this iMac.

which was odd because [my-iMac-name] was indeed the name

of the current iMac. I entered the password for the iMac user

account that I use daily and that was accepted. My daily user

account, by the way, is not an admin account.

I disabled iCloud for all apps except Books, Notes, Find My iMac, and iCloud Drive.

I connected the iPhone, I selected to sync all calendars and contacts,

and clicked Apply. It said:

Syncing [iPhone name] with this Mac will replace media from another

library on [my-iMac-name].

An iPhone can sync with only one computer at a time.

I chose Sync and Replace. This message came up as in the past:

"The information on the iPhone [device name] is synced with

another user account."

I chose Merge.

After the merge, some of the Calendars on the iPhone had

unusual names such as:

Calendar [my-appleid@p102-caldav.icloud.com]

I waited about and hour and reconnected the iPhone. When I selected

sync all contacts and calendars and clicked Apply, this message came

up again.

"The information on the iPhone [device name] is synced with

another user account."

One possible insight that setting up a new user on the Mac provided is that

when the alert says "another user account" it might be referring to

another user account on the Mac and not to another Apple-ID which is

what I have been assuming. That doesn't explain why the alert is

occurring, but at this point I think I will just live with the need to "manually"

select syncing for calendars and contacts. I'm happy the calendar and contact

apps are functional and the data is intact.

Thank you everyone who offered advice.