WebDAV sabre.io group throwing errors

[Rick Armstrong]

My team is trying to get WebDAV setup to allow users to share access to specific files if the users belongs to the same project, but hide/block access otherwise.

Reading the docs we think we're setting it up properly, but keep getting this error when authenticating.  The server.php file is mapped to .../dav/index.php (see attached file).

Anyone can have a look at requests in their favorite web debugger thusly ...

http://newui.proloop.com/dav/
rickatech
password (don't worry, nothing valuable here)

This XML file does not appear to have any style information
associated with it. The document tree is shown below.
<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">
<s:sabredav-version>3.2.0</s:sabredav-version>
<s:exception>Sabre\DAV\Exception\NotFound</s:exception>
<s:message>File not found: rickatech in 'principals'</s:message>
</d:error>
<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">...</d:error>

I've also posted this question here in case anyone would like to get karma points on ServerFault / StackOverFlow
http://serverfault.com/questions/840946/webdav-sabre-io-group

[Rick Armstrong]

Just FYI

My team is keen to bring on paid part time staff to help us out on this if needed, so feel free to reach out to me if you have some non-trivial kung fu that can help us.