We have officially deprecated the old Sandbox URL (https://sandbox-api.stuart.com)
The new and valid URL is:
https://api.sandbox.stuart.com
On March the 1st 2021, the URL https://sandbox-api.stuart.com will stop responding to your requests, so we encourage you to update your code as soon as possible.
Update on March the 2nd 2021: The URL is now officially deprecated and in the following days it’ll stop responding to your requests, without further notice.