But in their original post, the seller said:

You don't need to take any action and you won't be charged for this refund. We're contacting you about a return request your buyer opened for ASUS PRIME B550M-A WIFI AM4 AMD Motherboard.

This order was processed through Simple Delivery, so we handled the return on your behalf. You don't need to take any action and you won't be charged for this refund

So they have already been told it's sorted and not to take any action.

I would still recommend to do the live chat thing as that usually sorts it out straight away