Q: frequently Visited websites sync

hi,  i've got an ipad/IPhone and IMac with MacOS Sierra installed and all iOS devices updated to latest software but frequently visited website sync between iMac/iPad and iPhone not syncing properly on Safari.  How do I turn this feature off and back on again across all my iOS devices and MacOS Sierra on Safari ?  I've tried seach the internet but the tutorials and all based on older versions of iOS and OSX.

thanks in advance