I'm thinking now that the problem was with the data point 'MangoES_Disk_Percent_Used'. This fails to import, then all the watch lists, event handlers, etc that are linked to it also fail. It appears this also causes the entire DP hierarchy to fail to load. I believe I'll need to remove all references to this DP from the json file before importing. I understand tha a DP starting 'mangoES' doesn't belong on a GT mango, but there are other points like this (eg MangoES_Disk_Space_Remaining) that seem to be imported OK. Is there something in the import processing that's preventing 'MangoES_Disk_Percent_Used' from being created?