Migration assistant failed

I tried to upgrade from Yosemite to El Capitan, but that failed. So the staff at the local store did a clean install for me. Prior to that, my Mac's internal hard drive had been backed up using Time Machine, onto an encrypted external hard drive. However, Time Machine is unable to restore any of back ups (the timeline of previous backups shows up, but the Restore button is grayed out). I tried to use the Migration Assistant, but it quit unexpectedly. In the process, I was prompted to create a new user account, but I don't see it under /Users/.

Still, the backups are visible in the directory structure of the external hd (My passport). However, only some, not all of the directories are accessible. For example, I was able to copy Documents from the ext. hd to the internal hd, but Google Drive cannot be accessed. More detail in the attachments.

Please help obtain access to the directories whose access is currently blocked on the external hdd.