dodge carvan wont start and I have had parts replaced.

I took it to a mechanic they told me that the fuel pump and alternator needed
to be changed.I replaced the parts and the problem is still occurring. Now I
feel the mechanic is deflecting and  saying its the computer and I replaced
those parts for nothing and that its the computer and go to a dealer ship.
They told me the battery was good and have checked it twice. The car turns
over when jumped could it be the battery? Its a 2013 caravan so im kind of
hesitant that its the computer.