How to make a backup from data ona QNAP NAS

We have BE2010R3 running on a Windows Server 2008R2. In the network we have a QNAP NAS model 859. From the server you can access the data on the NAS. When you want to make a backup with BE from the data on the NAS you can select the NAS and see the directories on it. The NAS reports a seccessful login from the server. But in BE the directories shop up as greyed and you can not select them to show the files. So you cannot make a selection for the backup to be made. How can we make a backup of the data on the NAS to tape using BE?