iCloud Safari tabs Missing on Mac
I just updated both my iPad Air and iPhone SE to iOS 10.2.1, and since then, Safari on my Mac is no longer showing any iCloud tabs for my iOS devices.
The iOS devices are both showing the Mac's browser tabs, and both showing each other's but on the mac, there's nothing in the area where they'd normally show.
The Mac is running MacOS X 10.10.5 Yosemite, and Safari 10.0.3 (10.0.2 was also effected).
Disabling all browser extensions has no effect. Switching iCloud tabs off and on on all 3 devices has no effect, logging the Mac out of iCloud and back in has no effect, rebooting the Mac has no effect.
All other iCloud functions like bookmarks and reading list work, as does Handoff, Continuity, Airdrop etc.
Any suggestions?