iCloud tabs disappear in Safari, over and over

I still have the option in Customize Toolbar.

Do a backup, using either Time Machine or a cloning program, to ensure files/data can be recovered. Two backups are better than one.

Try setting up another admin user account to see if the same problem continues. If Back-to-My Mac is selected in System Preferences, the Guest account will not work. The intent is to see if it is specific to one account or a system wide problem. This account can be deleted later.

Isolating an issue by using another user account

If the problem is still there, try booting into the Safe Mode using your normal account. Disconnect all peripherals except those needed for the test. Shut down the computer and then power it back up after waiting 10 seconds. Immediately after hearing the startup chime, hold down the shift key and continue to hold it until the gray Apple icon and a progress bar appear. The boot up is significantly slower than normal. This will reset some caches, forces a directory check, and disables all startup and login items, among other things. When you reboot normally, the initial reboot may be slower than normal. If the system operates normally, there may be 3rd party applications which are causing a problem. Try deleting/disabling the third party applications after a restart by using the application un-installer or by using the developer’s uninstall instructions. For each disable/delete, you will need to restart if you don't do them all at once.

Safe Mode - About El Capitan also Sierra

Safe Mode Startup – El Capitan. also Sierra

If it works in the Safe Mode, try running this program when booted normally and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor. Please use copy and paste as screen shots can be hard to read. On the screen with Options, please open Options and check the bottom 2 boxes before running. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown.

Etrecheck – System Information

Try running the combo update. It installs all previous updates plus the new one, which can replace any files that may have become corrupted.

10.12.3 Combo Update

I'm having the same issue. Have turned of/on Safari in iCloud but the button keeps disappearing in my Menu as well as the Customize menu too. The off/on solution works, but likewise, it's a poor solution if one has to do it over and over again!

I updated to 10.12.4 but that isn't helping either!

Suggestions anyone?

I have the same problem, although my iCloud tabs icon does not disappear from the "Customize Toolbar..." menu. I just periodically look for it and it's gone from Safari, so I have to add it back. Very annoying.

Might be a corrupt .plist.

Do a backup, preferably 2 backups on 2 separate drives.

Quit the application.

Go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J. When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder. Select Library. Then go to Preferences/com.apple.Safari.plist. Move the .plist to your desktop.

Restart the computer, open the application, and test. If it works okay, delete the plist from the desktop.

If the application is the same, return the .plist to where you got it from, overwriting the newer one.

Thanks to leonie for some information contained in this.

Did you try resetting the sync on the device?

I suggested that in case you were syncing with an iPhone, iPad, or iPod.

It is a little drastic, but have you tried signing out of iCloud and then back in?

Have you tried updating to 10.12.4?

ALL THE TIME!!! I keep adding the iCloud button to the Safari toolbar but now with the 10.12.4 macOS update the icon is missing from the customize toolbar selections.