Problem statement
Regular users of a slack workspace were getting an error when installing a slack app associated with the custom oauth2 connection in Auth0:
You are not authorized to install -app name-, it is restricted for this workspace.
Solution
Even though this is outside of the scope of Auth0 support because it is related to Slack’s app management console, people can get confused thinking this is an Auth0 error.
Slack offers an option for workspace admins to require approval for regular members to install apps, which can cause this error. Disabling the setting on the Slack side is the solution as explained in the following docs: