Car died while driving and now will not start. What could it be?

It's either not getting spark or not getting fuel. If I'm not mistaken, it primes the fuel rail with pressure (check to see if it is) and then turns pump back on after the engine reports it's turning via crank sensor. So- do you have rail pressure when you turn the key on, but before attempting to start? If yes, you need to look at primary ignition next.

The camshaft sensor (above the starter) is failing or bad. Get a good new one. The cheap ones sometimes don't work. Make sure the leads to all sensors are clean, (use contact cleaner) properly attached, and not broken.

2000 Nissan Altima GLE my stepdaughter was driving Herr Nissan she said it start losing power slowly all lights came on in dash and died motor will turn over but will start I'm thinking it's the alternator it has a brand new battery it has well over 200,000 miles on it. Any suggestions will be helpful and it is automatic