After a long struggle, I was able to get the extension active in my environment, however I am now unable to upload files at all, receiving the "Sorry! We could not process your edit due to a loss of session data." warning when uploading any file.
Uploads directly from the target server work fine using the localhost address. I do not appear to be getting any problems with any other forms of edit, just file uploads, so I'm wondering if there is any known issue. The identified PHP session folder is populating with files.
Are there any other clues I should be looking for?
Running Windows Server 2012, IIS 8.5, MySQL, PHP 5.5.29, current mediawiki and NTLMActiveDirectory extension enabled.