Was this with Evri?
There has been some tech issue with wrong messages being sent out that sellers have requested returns, when this was not true.
Did you actually receive the item?
Your profile page is not showing for me but I'm guessing you are a Private seller and you used Simple Delivery for this transaction?
If so, message the buyer to open a case for item not received , and yes of course explain the situation was out of your hands and that many are experiencing this very frustrating issue. The item will be relisted if they wish to purchase the item from you again, and Evri delisted, so it will go with Royal Mail.
You will find the postage under SD for a single postal option will be higher. Personally if it was me, because of the inconvenience the buyer experienced, I would refund this excess postage cost, but of course that's entirely up to you.
I haven't seen any update if this issue with Evri has been solved, may be wise perhaps to deselect that carrier until issue solved ?
@andrew_carruthers2012