That is the mis-fuelling flap designed to prevent putting the wrong fuel in the vehicle. It popped because you put the fuel additive in and the flap read the end of the container as a wrong fuel bowser nozzle.
You should have a tool to reset it in your vehicle somewhere - sometimes in the top glove box and sometimes in the tool area in the rear.
See this LR4 vid on the topic - is the same a a RRS.
Garry
You should have a tool to reset it in your vehicle somewhere - sometimes in the top glove box and sometimes in the tool area in the rear.
See this LR4 vid on the topic - is the same a a RRS.
Garry