Horrible smell ??

Could be that your hose or your neighbors hose is not sealing to the pipe in the ground.
Been camped next to a few people with their 3" sewer hose just in the 4" ground sewer pipe with room for odors to escape around the hose.
Randu

You didn't leave the valve open did you? Smells will come up from the sewer if you don't close it.

Husband said no. But we did just realize that, you know when you fill up the toilet with water just by pressing down the pedal (?) on the floor? well it's filling up but the water is leaking down and not staying filled, we did not know if it just started that because we never paid attention to it.

Yep. That will do it. You need the water to seal out the smells. Hope you get it working. Try using a toilet brush and really giving it a good scrub down there.

Others have said, drop a little vegetable oil in the bowl, let it sit for a while, and let it soak. Add some water, then open and shut fast.. the oil will stick and lubricate, perhaps even help with sealing. It's not the nicest thing to have to do, but it's all part of rv'ing.

I just got back from Walmart in Vancouver, WA and bought a brush, I don't have any veg oil but can get some tomorrow. Bought some liquid deodorizer instead of the packets but I will get some oil and try that tomorrow and Thanks for all the great info (we got a lot to learn)

batteries can also cause a bad smell.

also you sinks will give off an odor if the "P" traps are dry.

Make sure your stove burners are turned off. Seems like we're getting a few posts about people accidentally bumping the stove burners and not realizing they are on. The Propane smell can sometimes smell like septic.

See if you can isolate the source of the smell. It might be coming out from the air admittance valve under one of the sinks and not from the toilet at all.

Could be your water heater. Have you flushed it and changed the anode rod lately / ever?