Credentials Fail for MS SQL Server Backup

Hi All,

I've just taken over a backup exec 2012 server and my main issue at the moment is that the person that set up the SQL backup, just did it as a file backup only - and had de-selected the MS SQL Server Instances.

I've tried adding them to the backup, but the windows logon account credentials that I am using fail in the test credentials screen

I can log in to the SQL server using the same credentials, and the user has the server roles of serveradmin and sysadmin assigned to them.

What am I missing?