I spoke with you about your project a few weeks ago on a conference call.
I can't speak to the error you are receiving, but make sure you have access to the top level group and an admin (most likely security issue).
When I spoke with you about zones, what I was saying was you should probably just change the "activeTo" property of the zone so it will expire. You most likely don't want to remove the zone because you want to retain your history in Geotab for reporting.
I have a Feature Request in with Geotab to add a "activeFrom" property on the ZoneSearch object and to provide a filter in the UI so you don't have to see the expired zones. However, I know you are looking at more than 500 zones anyway so that UI part does not matter to you so much.