Cannot restore.

I'm evaluating Zextras with Valid, Trial license on Ubutu 10.04.4 LTS, Zimbra 7.2.0_GA_2669.FOSS. Everything works great except that I cannot restore. I have initialized backup and run Fullscan successfully. However, when I clicked restore, I always got an error "The Restore operation cannot be started as Zextras Backup's destination path is not initialized. ...". I checked /opt/zimbra/backup/zextras/ and found many backup data.

What do I missed? Please help.