Tickets.com Approved My Refund, Then Denied It Without Explanation

I purchased a ticket from Tickets.com for a flight to South Korea but was unable to travel. I canceled my return flight and patiently waited 75 days for a partial refund, which was eventually approved. However, now Tickets.com has suddenly called me, claiming that the airline denied the refund—yet they refuse to provide a reason for the rejection.

How is this possible? If my refund was already approved, why was it later denied? How was the refund amount determined, and why did it change? Without any transparency, how can I avoid this issue in the future? This is completely unfair! Tickets.com, I demand a clear explanation and my refund processed immediately!