Issue
When using Quest's Mextalogix Essentials for Office 365, Nintex workflows fail to migrate with an "unauthorized" error.
Resolution
Ensure that you have whitelisted https://nintex.onmetalogix.com. You can check the availability of this services URL by visiting https://nintex.onmetalogix.com/nintex/version, and you will see a result similar to the screenshot below:
