How to fix invalid_redirect error message in Canvas

Symptom

When trying to insert H5P content into Canvas through LTI 1.3, the following message is displayed:

Link Resource from External Tool
{"status":"bad_request","message":"Invalid redirect_uri"}

Reason

There's something wrong with the LTI Developer Key's Redirect URIs.

Solution

1. In Canvas, go to Admin->Developer Keys
2. Locate the H5P developer key, and select Edit
3. Check the Redirect URIs field. It should contain https://<subdomain>.h5p.com/lti/launch, where <subdomain> shall be replaced by the subdomain of your H5P account.