User 'guest' does not have permission to run DBCC

Good day to you.
I try to attach a database mdf file to Microsoft SQL server 2014 on Amazon Elastic Computing Cloud, EC2, but fail with the following message, 
"User 'guest' does not have permission to run DBCC checkprimaryfile. (Microsoft SQL Server, Error: 2571)"
The ID I use to REMOTE login has administrator rights and I have chosen to "run as administrator"
Please help, and thanks.