Running 5.30 on my RPI2 happily until recently, but having changed changed my file location to a router share (Netgear ReadyShare) the Rebuild Library doen't seem to function. I have a green tick in the mount box using the same IP and folder name that seems to work in a browser so assumed that part was ok, however noticed the log contains the two lines below:
CIFS VFS: Error connecting to socket. Aborting operation.
[CIFS VFS: cifs_mount failed w/return code = -101