Item level recovery failed for SharePoint 2013

I have DPM 2012 SP1 Rollup2 and I wanted to recover Sharepoint 2013 Site (Single Sharepoint Server with SQL 2012 SP1 Database).

I get this error:

DPM was unable to query the unattached content database SHAREPOINT\SharePoint1. Exception Message = Login failed for user 'C\spAdmin'.. (ID 32018 Details: Unknown error (0x80131904) (0x80131904)).

C\spAdmin user is sysadmin on Sharepoint SQL Database.....

I don't know what is wrong?

Thanks for help in advance!