Def system issue on a 2016

Hey guys, I just bought a 2016 f350 CCLB 4x4 DRW. Truck had 15.400 on it when I bought it about 3weeks ago, and has 18,700 now. So I am still really new to this thing. Approximately 700miles after buying the truck I filled the def tank up, the display said def below 1/2 and I have heard others say keep it full. Fast forward to yesterday, 2500miles of driving later. I hook up to the trailer to go grab some materials, hit the self diagnosis thing to see what trailer brakes are set at etc... read out says diesel exhaust fluid level ok. I drive about 15miles. Stop turn the truck off load up, get back in and when I turn the key on it says diesel exhaust fluid range 500miles. This seems odd that it never registered below 1/2, and that it miraculous happened at a key cycle and not while driving. None the less, I grab a can of def and fill it up. It takes almost 2.5 gallons but doesn't reset and continues to count down. Called the ford dealer, and they are saying that they have never heard of a ford having a def tank issue and that I just need to put more in it. 2.5gallons for 2500miles seems about right from what I have heard others say, and it seems like if it did get low it should have shown below 1/2 at some point or for a while at least.do these kind of little issues sound familiar? Am I doing something wrong, how long does it take to reset the count down? I have only driven about 15miles since refilling but would think it should have cleared by now. Any insight would be great. Thanks in advance, Sean

ive had sending unit/pump/heater issues in the past. Gotta pull the box off to swap it or drop the DEF tank. part is around 1500 iirc. Forscan should help you pull a code to help narrow it down.

My service truck does the same thing. Mainly in colder weather though. I haven't had it happen to often in the summer. But anyways. Sometimes it takes a couple of key cycles for it to reset. Then I also will keep it topped off. For awhile and it seems to go away. Kind of a pain in the rear but until it gets worse I won't do anything about it.

Emissions warranty should take care of it, IMO.

Yeah, it's not very cold out here even in the winter. The truck is low enough mileage that it should be under warranty regardless. It's been about 6 key cycles now and 40 miles. /9 I'll keep an eye on it and head to the dealer if it doesn't clear up.