The submit score button is not displayed to the student.
"labsim_allow_outcomes" is redundant and not necessary for an LTI link to be graded in Blackboard.
Check "Enable Evaluation" to enable the submit score button.
When examining an LTI payload created by Blackboard with outcomes or scoring enabled. The POST LTI payload has an "lis_outcome_service_url" but no "lis_result_sourcedid".
The user launching the LTI activity does not have a Student role in the class.