Ah, it looks like you have a key picked up as an item in your stack. (see the white outline on the key) You should be able to cycle through to the fuel items with the scroll wheel, or drop the key by looking at the ground and right clicking. If you use the key on a key slot like you the one you interacted with in the opening, that will also consume the item and free you to use the remaining fuel items.
Nice catch though! I think we missed this being a tricky interaction since all of us were used to the inventory system, maybe we should have had the key in the left hand and fuel on the right or something similar that prioritised the fuel over the key in situations like this.
