If you need DMX WebDav enabled on your website, you must open a ticket with PowerDNN to have the follow server customization done:

Add this to the Web.CONFIG:

<!-- allow large file uploads -->
<httpRuntime useFullyQualifiedRedirectUrl="true" maxRequestLength="51200" requestLengthDiskThreshold="51200" />

This must be done in IIS:

If you don't want to do this then I have the latest DMX module avaiable which I think you may be familiar with. It has some install requirements also. They are:
1. Log in as administrator on your server
2. Go to the IIS control panel and call up the properties of the web site of the
installation
3. Go to the ‘Home Directory’ tab
4. Double click on the ‘.axd’ extension mapping in the ‘Application Extensions’ list
5. Change the Verbs list in the ‘Limit to:’ text box to read:
GET,HEAD,PUT,OPTIONS,PROPFIND,PROPPATCH,COPY,MOVE,DELETE,MKCOL,LOCK,UNLOCK,DEBUG
6. Make sure you leave the rest untouched (check illustration)
7. Click OK three times to exit the Application Configuration and website
properties
8. Go to the ‘Web Service Extensions’ node of your IIS panel
9. Make sure WebDAV is ‘Prohibited’. DMX integrates its own WebDAV, the Windows WebDAV conflicts with this.
10.  Step 1 is done

11. Log in as administrator on your server
12. Go to the IIS control panel and call up the properties of the web site of the
installation
13. Go to the ‘Directory Security’ tab
14. Under "Authentication" click EDIT
15. Uncheck "Integrated Windows Authentication
16. Click OK twice to exit the application configuation and website properties.
17.  Step 2 is done