Are you using the service account with stored credentials? If so I'd sub in my own credentials to isolate the issue.

I would agree with Roger, this is a bit of an odd issue to see for one set of credentials. I would try your own or another account you access SharePoint with to see if you get the same thing.

Did this just happen once, or has it happened a number of times?

Hi,

This is the first time I am using the service account and its giving me that error. My account works. Does this mean Ser.Acc don't have sufficient privileges?

Does the SA have the same privileges you do on the site?

I am unsure. But we maintain a separate set of permissions for SA as it will be only used in non-interactive login scenarios such as putting login inside workflows, etc

I will check with IT in this case. Thanks!

You should be able to check permissions right in the site permissions as in the screenshot below.