So Safari 11 broke iCloud tab syncing
So, in typical Apple fashion, the brand new Safari 11.0 for macOS Sierra 10.12.6 completely broke iCloud tab syncing. Our other devices (iPhone and iPad running iOS 10.3.3) can no longer see our open tabs from our Mac. Our Mac can still see our open tabs from the iPhone and the iPad, but our iPhone and iPad can no longer see our open tabs from our Mac. This was working perfectly fine in Safari 10.x for macOS Sierra, but as soon as the Safari 11.0 update came along, this functionality was completely broken by Apple.