Your prior posts suggest that you've checked power to the pump/motor, downstream from the relay and found that when the switch is "ON", you have power (13v) to the pump/motor and when the switch is "OFF", there's no power (0v).
That suggests, to me, that you have power to the relay, the relay is working properly and that the failure is the pump/motor.
Motors do fail. That pump/motor assembly lives its life immersed in sewage water.
When I replaced the macerator on my '18 Entegra Anthem, the part that I needed was a Thetford 97518 Pump Replacement w/ Tank Housing. That may, or may NOT
, be what you need. IF that's what you need, I found the best price here: https://www.boatandrvaccessories.com...75f849bb&_ss=r
5 in stock, free shipping, $246.38
That comes as the whole gray box assembly with the pump/motor inside. I couldn't source just the pump/motor.
IF it's possible for you, depending on the installation, to open the gray box to access the pump/motor assembly, I found it much easier to not disturb the Fernco fittings and just pull out the bad pump/motor and replace it with the new pump/motor.
Again, I'm not familiar with the installation on your Newmar. On my Entegra, it was much easier to leave the gray box in place and just swap the pump/motor with the gray box in place. Not particularly easy; just easier.