When you create a sandbox from a live production org. Salesforce will copy across the meta data, meaning that the live Asperato configuration gets ported to the sandbox.
You need to amend the Asperato ONE Custom settings so that you can then create or attach a test Asperato ONE account.
Log in as an administrator and go to Setup.
Locate Custom Settings.
In the list of settings look for 'Asperato ONE settings'
Use the 'Manage' link to show the current settings and then 'Edit'
Remove the content of the field called 'Customer ID'.
(Note if you have an existing Asperato ONE test account that you want to link to then you need to enter the Configuration ID of that account in this field)
Make sure the field 'Is Running Live' is unchecked.
Make sure the field 'Server URL' contains the value 'test.protectedpayments.net'.
You can now go to the Asperato Setup tab that is part of the Asperato ONE application and follow the instructions to create a new test account.
If the screen is asking for an API key then contact firstname.lastname@example.org for assistance and include the Configuration ID.