Not sure about the newer Newmar tank layouts , my DS, has the water bay on the left side, in front of the rear axle, with all the controls and sewer dump, on the opposite side of the coach there is a tool hanging peg board. That peg board has to be removed to access the tank sensors. Mine are stuck to the side of the tank and two fell off , so that may be your problem .
Haven't had to replace them so can't help if you require new .
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.