This usually occurs because the consumer key and secret are wrong.  In many cases, your browser's password manager may be automatically filling in the secret with your Moodle password, rather than using the secret that your Moodle administrator configured. 


To fix this, you will need to edit the LTI link as follows: 

  1. From your course, toggle into editing mode.  Then, click the Edit link and click Edit Settings.
    Screenshot of "Edit Settings" being clicked on a module from course edit mode
  2. On the Tool Settings page, click Show more...
    Screenshot of "show more" link
  3. Make sure that Preconfigured tool is set to Automatic, based on launch URL.  Then, make sure the Shared secret field is blank. This will ensure that the password your Moodle administrator configured for the tool is used.
    Screenshot of Tool Settings page with an arrow pointed at the "Preconfigured Tool" field and the "secret" field.


  4. Click Save and return to course to save these settings.
    Screenshot of Tool Settings page with an arrow pointed at "save and return to course"