Application Link Configuration - Incoming Authentication

[Qibin Tan]

After setting up the application link for a third-party tool, we will need the incoming authentication page to finish the OAuth step. But that page shows the bitbucket refused to connect error. We've whitelisted the IPs from the third party and can HTTPS to the site directly through the bitbucket server. However, it still shows that connection refuses error. 

Any help would be much appreciated!

Thanks