Hello again Simli27,
The sign-in credentials are not your currect crentials but the stored crentials when you ran the discovery.
So it could be that you have no stored sign-in credentials for your servers.
You can check this at the second tab(tools and links) from the server you selected ad click on credentials. Here you will find snmp and/or wbem credentials and if you have a trust with the selected server.
If you add an account with admin rights to your server to the global protocol settings in Sim and run a identify, the credentials should be added to the server credentials. Do not use your own account for this as it will lockout your account when you change your own password and the identify runs from Sim. Best case you should create a service account for that.
Kind regards,
Andrew