Hello WAGE1970
Welcome to VMware Communities.
From the error reported I see that the information entered to add vCenter endpoint is incorrect.
Please follow the below steps to connect vCenter to skyline.
1: Please enter fully qualified domain name of your vCenter.
2: Provide the complete domain username ( E.g.: Administrator@vsphere.local or any other user )
3: Password of the domain user.
4: SSO configuration:
If you have embedded Platform service controller no need to enter the SSO details, In case of external Platform service controller ( Custom SSO E.g vsphere.local ) please fill the SSO details by enabling the custom SSO configuration and try adding the endpoint.
In case if you have any further concerns we can connect over zoom session so that I can assist you to add vCenter to skyline.
Sincerely,
Triveni Shanwad
Skyline Support Moderator