Run your site with public access (use ngrok or similar). Better in a just created site than in a existing one that may have already other tools configured. To replicate the issue: Set up an LTI 2 connection to the saLTIre test tool: As a system administrator, navigate to the Manage tools option for the External tool plugin (at /mod/lti/toolconfigure.php) Enter https://lti.tools/saltire/tp in the Add tool box and click on the Add button Click on the Tool Proxy button in the top navigation bar Click on the Submit button Click on the Yes button to activate the tool Add a link to the tool in a course: Navigate to a course as a teacher Turn editing on Click on the Add an activity or resource link Select External tool Enter an activity name (e.g. Memberships test) Select saLTIre tool provider from the list of preconfigured tools Click on the Save and return to course Make a request to the link-level memberships service: Click on the link added to the course Select Membership v1 from the drop-down list of services on the top navigation bar Click on the Read button Verify that a message of "Sorry, an error occurred" is NOT displayed, but a dialog with the number of members retrieved is displayed. Use the "Last service request" (Response tab) option on the View drop-down list to view the response received. Verify the correct spelling of the "givenName" element and the inclusion of the "ext_user_username" element in the resulting json.