Advice needed regarding refund request

Looking for advice regarding a canceled non-refundable business class ticket.

I had an unexpected surgical procedure that prevents me from traveling (lifting restrictions, sitting for more than 30 minutes etc) that will last well into my originally scheduled trip to New Zealand Nov 8-Dec20,2026. My travel partner ticket booked on the same confirmation was also canceled.
The ticket was originally purchased April 18,2026.
United issued travel credits valid until April18,2027.
The problem is that although I’ll likely be medically cleared to fly by then my 6 week itinerary in New Zealand cannot be booked due to fully booked hotels, tours, etc. I booked my original itinerary nearly 7 months in advance.

Is there any hope that United would extend the flight credit out to Nov-Dec 2027 to allow me to essentially rebook my originally itinerary?

Or am I pretty much out the $18k spent for biz class for my bucket list trip? I have no way to know now whether such a trip could be executed in March/April’27 given the post op recovery.

Oh I canceled my tickets 7 weeks prior to departure, as soon as I knew. Giving United plenty of time to resell at higher rate.