That still sounds like fuel, like it started after sitting and then when the collected fuel was used up it died again.
Do you have a scan gauge?
Can you hit the battery combiner switch to test if more power would help?
Get some spray starter - ether - in a can and spray it into the air intake while cranking.
It might help to take the doghouse cover off and see if you see anything obvious while cranking.
Tomorrow if it won't start it's time to either have it towed to a repair shop or have a mobile mechanic come to you.
Air, fuel, spark are the only things it can be - but there are tons of ancillary items that meter all of the above that can stop working i.e. coils, fuel injectors etc.
2017 Winnebago Adventurer 37F
2016 Lincoln MKX Toad