Hey Peter,
We’re looking into this, and we have an understanding of the underlying issue. We recently enabled SMB2 on ROCK, but I think Windows may be blocking “guest” access (as described here). This is probably something we will need to fix, so I don’t think this is related to your setup.
For now, try this workaround: Go to Control Panel > Programs and Features > Turn Windows Features on or off > confirm the the box for “SMB 1.0/CIFS File Sharing Support” is checked.
Let us know how that goes. Thanks!