IF your tank is 1/3 or less, the autofill will work. As David said,you need to have both the lever in autofill and the autofill enabled in the control panel. Mine only filled to full at the factory with the technicians watching when I went there to get it fixed. For me it always filled to 2/3 and quit. Then I put it in manual mode and waited for water to come out of the overflow on the opposite side of the coach. Then when you take off, the water would siphon out to 2/3. There was a fix posted here about drilling a little hole in the overflow tube to stop the siphon which is a great idea but didn't get it done before I sold the 4018. If my 2018 does the same thing, I'll know how to fix it. Maybe the autofill will actually work on my new one, and maybe it will work for you on yours. Hope that answers your question and happy motoring!
Bill & Chris Bélanger (KI1Z)
'04 Georgetown XL > '17 4018 DSDP FL > '18 DSDP 4327 K2
2018 JL Wrangler Rubicon 2 Door