Fillz doesn’t re-list items when credit cards are rejected. You must manually increase the quantity of the items in Fillz. Once you have done this, Fillz will automatically export the items back to all of your active marketplaces.
A quick way to re-list an item when you are looking at the order in Fillz is to click on the SKU, edit the quantity, then click Save Item.
Be sure to move the order to Cancelled status in Fillz to avoid fees.