3808072 - OpenAPI: Award Scenario Creation API returns "Given supplier user not found in the given event" despite contact present

I'm trying to create an award scenario using the Event Management API, but it is failing with the error Given supplier user not found in the given event, even though the supplier contact is available in the event and can be awarded manually through the user interface.

Award Scenario Creation API, supplier user not found, invitationId, supplierInvitations, POST /scenarios, GET /supplierInvitations, response team disabled, email identifier, supplier contact, sourcing event, REST API error, Ariba Sourcing API, award scenario, contact email, incorrect invitation id , KBA , BNS-ARI-SS-API , Strategic Sourcing - REST API , Problem