There might be a case where your Anypoint Studio is not connected to Anypoint Platform to establish a connection with API manager for Auto Discovery. So disable the auto-discovery in locally for testing purpose or set up Anypoint Platform credentials in Anypoint Studio to have a proper connection for API Auto Discovery.

For Disabling,

• Try to comment on the Auto Discovery XML config from Code and see how it works or not

• Or pass the below VM argument in Anypoint Studio

   -Danypoint.platform.gatekeeper=disabled
  

Note: Disabling is only for testing purposes.