Lync 2013 – installing databases failing with Access is denied

Had this unusual issue recently while deploying a Lync 2013 Enterprise infrastructure. All the Lync 2013 databases installed correctly, except for the rtcxds database, which is arguably the most important one. The generic error was system error 5: Access is denied.
"An internal error has occurred while trying to create or update the database."


Weird. I have all the correct permissions. I am a domain and enterprise Administrator and a member of CSAdministrator and RTCUniversalServerAdmins (This was a Lync 2010 to Lync 2013 migration)

 
So I started looking around at permissions. Here's the file I cannot access via the C drive:



 
And here it is via the C$ share – it's not even showing!



 
I didn't screen capture the permissions, but I didn't have rights to view permissions on the file either. The same was true for the rtcxds log files as well.

 
The resolution:
Rename the rtcxds.mdf and rtcxds.ldf files to _old, and then reattempt installing the databases. This recreated the files within the CsData folder, set the correct permissions, and then the database install succeeded. Never did find a root cause for why this one occurred.