\uD83E\uDD14 Problem
While adding a new GitHub organization to your Confluence does not show any authorization option and configuring macro details on the page results in 400 error.
\uD83C\uDF31 Solution
This issue happens mostly due to an active session of Github in your browser. By default, Github Macros for Confluence takes the current session to access any organization/data.
Log out of any active session of Github in your browser.
Follow the steps mentioned https://appfire.atlassian.net/wiki/spaces/GMFC/pages/150241327/Configuring+Github+Macros+for+Confluence+Cloud#:~:text=and%20public%20repositories.-,Configuration,-Go%20to%20the to add a new organization.
Then configure the confluence page by reviewing https://appfire.atlassian.net/wiki/spaces/GMFC/pages/150241327/Configuring+Github+Macros+for+Confluence+Cloud#:~:text=Github%20File%20Content-,Using%20the%20macro,-Here%20is%20an to show data.
You will need administrator access to configure this