Symptoms
The request failed with HTTP status 401: unauthorized error when loading form
Diagnoses
I've recently used the Package and Deployment tool to migrate one of our production workflows to the development environment. There were a few errors in the deployment about a SmartObject (I've attached the log) but I don't think these should of caused the error I'm receiving.
The error when I load the form in runtime is: "The request failed with HTTP status 401: unauthorized".
I can load the form in edit mode with no issues.
Resolution
ServiceInstance switched to ServiceAccount. The ServiceInstance was previously set to Impersonate, which caused issues.