We reinstalled our Webwork server from scratch in the fall and added a SSL Certificate too. After these changes our LTI connection with Blackboard stopped passing back the grades to Blackboard, though login was still possible using a LTI link.
After looking around the system, we found out that the problem was with the handshake between the systems. It seems Blackboard had a weaker security key. The university just updated the systems and now Webwork is passing back the grades again to Blackboard. But the following warning message always appear when a user submit an answer for a problem in an assignment for the first time and then it doesn't show no more.
Anyone has any idea what is causing this???
WeBWorK has encountered warnings while processing your request. If this occured when viewing a problem, it was likely caused by an error or ambiguity in that problem. Otherwise, it may indicate a problem with the WeBWorK system itself. If you are a student, report these warnings to your professor to have them corrected. If you are a professor, please consult the warning output below for more information.
- Argument "success" isn't numeric in subtraction (-) at /opt/webwork/webwork2/lib/WeBWorK/Authen/LTIAdvanced/SubmitGrade.pm line 337."