If you can’t reach it, you have to take that chrome cover off. Mine takes a pry bar and slowly prying it off inch by inch. It is easy to bend it so you have to be patient. I have also removed them with a super large screwdriver and hammer, but I find that more difficult. After you get it off, you may be able to position the valve stems so that when you put the cover back on you can reach them.
__________________
|