What can I do if the travel agency fails to rebook my ticket due to an emergency?

I would like to seek advice.

I bought a ticket from an agency but due to emergency surgery (bypass surgery) of my husband, I am unable to fly back home.

Two days before the flight, I called the agent and advised her of my situation and was advised that the ticket can be rebooked.

I promptly said to rebook the flight and a medical certificate has been provided. The flight was on 22 June 2023 and to this date, the issue has not been resolved between the agency and the airline.

And now they are requesting a marriage contract copy which I provided.

Appreciate it if you can please advise me on the best way forward.