Explanation
Before taking any further action, it is important to verify that the problem reported by the users is the same as the one that prompted the firmware upgrade. It is possible that the firmware upgrade did resolve the original issue, but a new or different issue has arisen with similar symptoms. By gathering additional information from the users, such as error messages, screenshots, logs, or network traces, the technician can confirm or rule out this possibility and avoid wasting time and resources on unnecessary steps.
Reopening the service ticket, requesting a new maintenance window, and rolling back to the anterior firmware version (A) is a possible option if the firmware upgrade did not resolve the original issue and caused more problems. However, this should not be done without first verifying that the users' concerns are related to the firmware upgrade and not a different issue.
Employing a divide-and-conquer troubleshooting methodology by engaging the firewall vendor's support is another possible option if the technician needs assistance from the vendor to diagnose or resolve the issue.
However, this should also not be done without first gathering additional information from the users to narrow down the scope of the problem and provide relevant details to the vendor.
Escalating the issue to the IT management team in order to negotiate a new SLA with the user's manager (D) is not a relevant option at this stage. An SLA (Service Level Agreement) is a contract that defines the expectations and responsibilities of both parties in terms of service quality, availability, performance, and response time. Negotiating a new SLA does not address the root cause of the issue or help to resolve it.
Moreover, escalating an issue to management should only be done when all other options have been exhausted or when there is a significant impact or risk to the business.