I see no responses so far so lets stir the pot a little.
Sounds like you might have two problems........how to get the tail light lens cover off (I assume there are no screw heads visible on your lens cover) and then once you get the cover off, how to verify you have a bad LED lamp (or something else like corrosion perhaps). I canít really council you on either with other than guesses, but when I search the net on your coach I get the following info (which may be of no use, but......): says for 2014 to current: Note this happens to be a UK eBay site
If you have this style wrap around lens cover it says that it uses the following lamps:
PY21W R5W P21W x 3 Excl. Bulb & Holder
If that is true, this is a LED lamp with bayonet base I believe times 3 in each lens unit. So if you can get the cover off I would assume you could swap one working lamp for the non working lamp to at least determine if it is a burn out that needs replacement. If this is not your lens then you can ignore my response.
Not sure how to remove the lens cover though if no screws are visible and no easy internal access to nuts holding the lens on is possible.