What does "Host busy..." error mean?

“Host busy” is an indication that you have a sync session already in progress. You may already have an active session from that computer, or some other computer which you setup to sync on a schedule. Once the sync session is complete, the host will no longer be busy, and your sync should succeed. In the event of a sync error, your status may be left as ‘busy’. To overcome this, CoronaSync servers routinely monitor for old/idle sync sessions and remove them from the system. If you believe a previous sync session ended in error, it will be automatically reset in no more than 30 minutes, allowing you to try again.