@John_Lowe ,
I'm not sure if this is the same issue, but see the blue notes at the top of How do I access the Canvas test environment as an admin?
One of the items there says:
LTI tools (External Apps) are typically not available in the outside the production environment. LTI tools may display in the test environment, but often they are only configured for the production environment. Using production-configured LTI tools in the beta environment will affect live data. If you have permission to edit LTI tools, you can confirm the configuration for a specific LTI tool in your course or account. Please contact your Customer Success Manager for specific questions.
Erin Hallmark has also made a couple of announcements in feature requests regarding LTI and them really only working in production.