Why has sync stopped working since upgrading the client operating system (for example to Mac OS X to Sierra High)? - Why has sync stopped working since upgrading the client operating system (for example to Mac OS X to Sierra High)? - Alfresco - Alfresco Sync Service - Alfresco/Alfresco-Sync-Service/3.11/Alfresco-Sync-Service/Alfresco-Sync-Service/Administer/Sync-Service-Admin-FAQs/Why-has-sync-stopped-working-since-upgrading-the-client-operating-system-for-example-to-Mac-OS-X-to-Sierra-High - 3.11

If SSL has been enabled on the Sync Service without provision for a signed certificate, then the clients may fail to sync content. The log files contain a message "SSL peer certificate or SSH remote key was not OK". Install the Sync Service with a valid security certificate or disable SSL for the synchronization server if required.