LTI 1.3 Deep Linking Issues

We have dozens of successful LTI 1.1/1.0 implementations, as it’s a simple config. But we don’t have any LTI 1.3 implementations, as we keep running into issues at every corner. Our current issue is the handoff. We received similar issues from two vendors:

Vendor 1
Invalid LTI Launch Type.
Status: 422 – Message_Key: InvalidLaunchType

Vendor 2

I know we are missing something but maybe another set of eyes. Our payload (scrubbed) is:


Would appreciate any advise.