My Safari bookmarks stopped syncing a few weeks ago between a MacBook, an iPad and an iPhone all on the latest betas.
I tried everything I could find online short of wiping the devices: Toggling Safari sync on and off, deleting all bookmarks and so forth. I even tried this. Still any bookmarks I add on any device will not show up on any other device.
YES I am signed into the same iCloud account, everything else is still syncing fine
YES I restarted the devices
YES they are up to date (all on the latest betas)
