checkboxtree doesn't save

I am sure I am missing something…

I have a simple checkbox. It appears well on the content editor.

However, the state of the checkbox is not stored after the update (at least the content editor shows them all unchecked again).

Where should I start?

I am running 6.7 with latest patches.

Found the issue. The XML Application was not “started” from the Workbench side. You have to press the green triangle to start.