New iPhone 17 Pro passwords not syncing on iCloud SOLVED!

New iPhone 17 Pro keychain/passwords not syncing on iCloud after switching from old iPhone 12 Pro via Quick Setup. All other devices, iPad, Mac Pro, etc all were OK.

After every attempt offered by Apple suggestions I.E.

Turn Off/On "Sync this iPhone" did not work kept toggling off after turning on.

Sign Out/In of iCloud account, etc.

Reset Network Settings

Erase all data and restore phone from backup did not restore ability to turn on passwords sync.

None of these worked.

Solution:

I had to Turn On - Advanced Data Protection

But this a a caveat: I needed to remove several old devices, a Mac 20" from 2010, Mac 27" from 2010 and an iPad from 2012.

These older devices would not allow me to turn on Advanced Data Protection.

Once Advanced Data Protection was turned on the Keychain/Passwords syncing basically turned itself on.

Nothing in any of Apples Solutions would work except this.

Hope it helps.