The auditor's best course of action in this situation is to notify the audit manager. The audit manager is responsible for overseeing the audit follow-up process and ensuring that audit issues are resolved in a timely and satisfactory manner. The audit manager can then decide whether to escalate the matter to higher authorities, such as the chair of the audit committee, or to accept management's decision and close the audit finding. The other options are not appropriate for the auditor to do without consulting with the audit manager first. Notifying the chair of the audit committee is a drastic step that may undermine the relationship between the auditor and management, and it should be done only after exhausting other means of resolving the issue.
Retesting the control is not necessary, as management has already decided not to implement therecommendations. Closing the audit finding is premature, as management's decision may not be aligned with the audit objectives or risk appetite. References: CISA Review Manual (Digital Version), Chapter 2, Section 2.4