BlogEngine.NET "update failed"

Mar 15 at 4:17 PM
Edited Mar 15 at 4:22 PM
I am trying to install BlogEngine.NET v3.3.0.0 on Windows 2008R2.

I am running against a MSSQL 2014 database, I created a blank database, ran the setup script, copied the dbweb.config into the blog folder and adjusted the connection string.

The front end seems to work fine, but every time I try to change ANYTHING in the admin area - the blog reports "update failed".

The IIS logs report a 500 error for the following request
PUT /blog/api/settings

The site is setup to run under a dedicated Application Pool (IIS AppPool/sitename.com), that user has been granted read access to the site web root, and full control of the App_Data and Custom folder.

URLScan is not running, nor is Modsecurity. UrlRewrite is installed but there are no rules configured on this site.

I'm running this in a subdirectory which is configured to run as an application. The parent web.config enables script access but that is the only entry.

I've tried using the native XML datastore, and also tried running it directly in the web root instead of a subdirectory as an application - same result.

Any suggestions I haven't already looked at? I would really like to get this running so I don't have to use WordPress ;)