I installed on a second device and it worked with Organisation on that - so I uninstalled from the first device and when I re-installed it worked there too.
Wrong path on PROPFIND. Sync fails.
Seems like your server (whichever it is) is returning the incorrect path
/dir/user/cal) to DAVdroid.
Thanks - and you are correct! DavDroid uses the path returned from the server root to dictate where to put the relative path on PROPFIND calls - changing it to dir/ results in it working fine. Great app.