Safari Tabs live-sync is working only in one-way

If you go to Safari/View/Show Tab Overview, do the tabs show?

Try setting up another admin user account to see if the same problem continues. Please post back on whether or not this worked. Also try the Safe Mode. Please post back on whether or not this worked.

Isolating an issue by using another user account 

Safe Mode - About

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. 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

If the log won’t post, try posting it in Pastebin and provide a link in a reply        Pastebin

If you go Safari/View/Customize Toolbar and drag the iCloud Tabs icon into the Toolbar, do the tabs show?

If you would post the Etrecheck report in PasteBin and provide a link, someone might be able to suggest something.

Try quitting the below and see if that helps. I would start with the firewall.

 com.synology.CloudStationDrive

com.tokaido.firewall.

I don't know. They are both 3rd party software you have installed.

Did it show with Safari/View/Show Tab Overview?

It may not help, but try running/posting the Etrecheck report.