I Cannot Generate a Return Code for My Mango Order

I am writing regarding a problem I encountered while trying to return an item purchased from Mango's online store.
On May 6, I ordered a handbag through the Mango website under order number F3N3L2. After receiving the product, I decided to return it within the applicable return period. However, when I attempted to initiate the return process, I was unable to generate a return code through the system.
Although less than one month had passed since my purchase, the return function did not work properly, preventing me from using the free return option that was offered at the time of purchase. Because I could not obtain a return code, I was unable to send the item back through the standard return process.
After experiencing this issue, I contacted Mango customer service for assistance. Unfortunately, I was informed that I would need to pay the shipping costs myself in order to return the item. I do not believe this is a fair solution, as the inability to generate a return code appears to be the result of a system-related problem rather than any action on my part.
When I purchased the product, free returns were presented as part of the service. I therefore expect to be able to exercise that right without incurring additional costs. A technical issue within Mango's return system should not result in customers losing the benefits and conditions that were offered at the time of purchase.
I respectfully request that Mango urgently resolve the return code issue associated with order number F3N3L2 and provide a functioning return method that allows me to return the handbag free of charge as originally promised.
I also request a clear explanation regarding why the return code could not be generated and what steps are being taken to prevent similar problems from affecting other customers.
I expect a prompt resolution and the opportunity to complete my return without paying any shipping fees.