I am currently testing our LTI 1.3 Tool with Canvas, and after the OIDC Third Party Login in which Canvas sends login parameters including the lti_message_hint, we redirect with a request to the authorize URL in order to request the id_token (per the LTI 1.3 OIDC flow). However, when we make this request to the authorize URL I receive the error: 

while(1);{"status":"bad_request","message":"Invalid lti_message_hint","error_report_id":170209301}

Even though we're sending back the exact lti_message_hint that we received on the OIDC TPL request (per the LTI 1.3 Spec). Any insight into why I might be getting this error would be greatly appreciated.