We've been using LTI to integrate a 3rd party assessment tool with our moodle. The 3rd party app is launched via a link on the course page, when complete a grade is sent back to moodle and stored in the grade book. This has been working preferably until a week ago.
The app still launches but the grades do not update. The error "Message signature not valid" is returned.
When trying the test tool http://lti.tools/test/tp.php , the grade doesn't return . We just get an error.