After looking at the free space, it appears that each folder on a Nexenta device has a hard size limit of 5TB.
I created a new folder and attempted to recreate the auto-sync and the service created and ran successfully.
To view the current space used in a folder follow the instructions below;
1. SSH as ADMIN onto the device you are replicating to.
2. SU to root permissions, but don't enter nmc. Your path should read something like root@devicename:/export/home/admin#
3. Run the command;
zfs list -ro spaceThis will display the AVAIL and USED sizes for each folder.