Here is the picture.
LTI provider is running on Moolde 2.6 (course with quizzes).
External tool is on Moodle 2.4
So from Moodle 2.4, you consume a course in 2.6. All is set to accept grades from provider, which is set to send grades.
It's just not consistantly running. I launched cron manually on both sides. Something seems broken.
Any idea where to look?