The two latest updates (version 3.1.11 and 3.1.14) of NextGEN Gallery (the WordPress plugin by, Photocrati) have introduces serious issues with the image upload functionality. As of right now, uploads from 3rd party applications that rely on the XMLRPC API (including my Lightroom plugin) are not working. There is nothing I can do from my side. I assume this would be fixed by Photocrati in a subsequent update. The issue has beeen reported to Photocrati, here is the forum post

4/2/19 Update

The issue has been fixed in NextGEN 3.1.17