Backup Exec 2015 installed on 2008 R2, SBS 2008 Domain, SharePoint 2010 Ent. on Server 2008 R2, SQL 2012 on Server 2012 R2, 2015 Agent installed on SP, shows Trust OK, Server Farm shows in Backup Exec, all resources show. When you attempt to set up backup job logon accounts fail, testing credentials yields "Server is not trusted". Gone thru all typical logon account issues. No problem with SQL server and I can backup the SharePoint server files and system state.