Cannot save Credentials on a secure server in ArcGIS Online

[KarenLizcano1]

I cannot save the credentials for a secured service from a stand alone 10.8.1 ArcGIS server in ArcGIS Online.  I can add the service, without saving the credentials.  I can access the data once I manually type in the service credentials but I cannot save them in AGO.  Any ideas? 

[JakeSkinner]

Hi @KarenLizcano1 the service may not be externally accessible?  For example, are you able to access the service URL when you are not on your network (i.e. outside of your firewall)?  The service will need to be externally accessible to store credentials.