Please, Could you give more context about your integration?, for your previous comments I recommended that you check this OAuth Integrations | Developer Documentation | SmartThings. but if you share with me more context I will try to help you in a better way.
Now, after browsing through the community a bit, I’ve found the following URL: https://api.smartthings.com/v1/oauth/authorize
After setting up the right redirect URI on my app, everything worked well and as expected.
So it was mostly confusion caused by the API docs, it would help maybe to alter the OAuth docs a small bit (to make it a bit easier).
Hello
It seems there’s an issue with the SmartThings API endpoint not resolving correctly, which is causing problems with authentication and authorization. To address this, I would recommend reaching out to SmartThings support or checking their community forums for guidance on resolving this specific problem.