If an error dialog appears when you try to setup Asperato, it may be because you didn't allow the remote sites during setup.

To check this, from Setup, enter Remote Site Settings in the Quick Find box, then select Remote Site Settings. This page displays a list of any remote sites already registered and whether they're active. This is what you should see if the remote sites are configured correctly:

If not, the "Active" checkbox may be unchecked. If that's the case, you'll need to hit the "Edit" link by each remote site to activate it.