If you experience authentication issues after configuring OAuth, it is recommended to use an API test tool such as Postman to bypass the CIC Document Upload feature and directly test Guidewire. This will help you determine whether the problem is caused by the configuration of your CIC Document Upload feature or the configuration of your Guidewire Home application.
Enter the information provided by Guidewire in your API test tool and verify whether you can send a request without receiving an error. If an error is returned, the issue is caused by your Guidewire configuration - see Configuring Guidewire Home. If no error is returned, the issue is caused by your CIC Document Upload configuration - see Configuring the CIC Document Upload Feature.