Failed to start Core Sync

File Sync Links that may help... all the links I have, since I don't know the cause of your specific problem
-About cloud storage https://helpx.adobe.com/creative-cloud/help/about-cloud-documents.html
-FAQ https://community.adobe.com/t5/Get-Started/Helpful-Links-FAQ-Where-can-I-find-links-about-managing-and/td-p/7570118
-http://helpx.adobe.com/creative-cloud/help/sync-settings.html
-http://helpx.adobe.com/creative-cloud/kb/arent-my-files-syncing.html
-sync and email link https://community.adobe.com/t5/Get-Started/Email-link-of-file-in-personal-CC-folder/td-p/5944719
-an overview of assets https://assets.adobe.com/files
-File sharing https://community.adobe.com/t5/Get-Started/Does-Creative-Cloud-support-sharing-videos/td-p/7113392

Let's try this in the Creative Cloud Services forum, which is the appropriate forum for issues affecting CCS as a whole.

The Using the Community forum is for help in using the Adobe Support Community forums, not for help with specific programs. Product questions should be posted in the associated product community.