If you're using a load balancer, set the dsync.service.uris property to point to the address of the load balancer in alfresco-global.properties.
For example, if a load balancer is set up to run on http://172.29.102.168:9999/alfresco, modify the alfresco-global.properties file to include the following:
### DesktopSync ###
dsync.service.uris=http://172.29.102.168:9999/alfresco