Myntra.com — Product Exchange cancelled due to internal reasons

I ordered one pair of heels of London Steps from Myntra on 18 dec 2021, when I received it the size was small for me so I placed exchange request for another size. The request was approved and the exchange was expected to be delivered by 30 Dec 2021. Today I got message that exchange is cancelled due to internal reasons. WTH. How can you cancel the exchange without any valid reason. And the product was allowed to be returned or exchanged within 30 days.
Why would someone order from you if you cancel exchange like this.
Please accept the exchange and deliver the correct size of heel.