i had a similar problem at first, but "the other way around", when i tried to request fluids at a fluid depot and couldn't get a selection window with a choice of fluids :-)
... spoiler ....
this was easy and nice to setup after finding out that there are two different depots to supply items and fluids (the "supply depot" and the "fluid depot" which maybe better should be called "fluid supply depot") and only one requester depot for both items and fluids; and that fuel is distributed with a similar but separate system, using fuel depots as supplier and the request depots as "automatic" requesters which request an amount of fuel depending on the number of their drones, transported by the drone(s) in the fuel depot.
