When a project deliverable is not fulfilling the business case requirement, it is important for the project manager to understand why this is happening. Analyzing the business benefits criteria and assumptions (Option C) can help identify if there were any discrepancies or misunderstandings in the initial planning stages. This could include reassessing the expected benefits, costs, risks, and strategic alignment of the project.

Additionally, scheduling a project review meeting to analyze the root cause (Option E) can provide valuable insights into what went wrong. This could involve discussions with the project team, stakeholders, and possibly the operations team who are now handling the deliverable. The goal of this meeting would be to understand the root cause of the issue and to identify potential solutions or improvements for future projects.