help 08 f250 wont start

[nussford]

Ok this my dads truck, he just recently past away so the truck had been sitting for about amonth maybe a little longer. 45000 miles no mods done. Go out to start it to get ready to wash all the pollen off of it, and it wont start. I thought maybe the batteries was weak so I put a voltmeter on it and said 13volts and cranking drops down to 11ish. So I think the batts r ok then. Bout a half tank of fuel. So I noticed when I crank it and it fails to start in the information display the oil can pops up. What do I need to do to get it started,what do I need to check.