Follow these steps to connect Box via the StackOne Hub successfully.
Log in
Go to the Dev Console
Create New Platform App
Select App Type
Enter App Details
Select Authentication Method
Copy Your New Client ID
Copy Your New Client Secret
Add a Redirect URI
https://api.stackone.com/connect/oauth2/box_iam/callback
Then click the Add button.Select Application Scopes
Save Your Application
Enter Credentials
Approve App Connection