I drove by Maxima one day and then the next day wouldn't start. I bought a new fuel pump filter and sending unit.still doesn't start but cranks.

 

Check for fuel pressure maybe the line came off!

 

check your electrical grounds and wires leading from battery to starter for corrosion.

 

Does it crank but not start? If so it's the starter. Yes it's the starter, especially if it's an aftermarket FLAPS part (autozone, oreillys.)
My 99 maxima had the same exact issue- for reasons unrelated to the starter (it was the NATS system shutting down the fuel injectors) my car suddenly would not start, but I didn't realize it at the time so I bought a replacement starter at OReillys. Of course that didn't fix the issue, but after I did track down the issue and get it fixed, about every 3 months the car would just konk out and not start. I finally discovered (after replacing the starter 3 times) that the OReilly's replacement starter only had 10 teeth on it whereas the OEM Nissan starter had 11. This difference caused the OReillys starter to continually slip on the torque converter and would eventually burn out the starter motor in about 3 months like it was on a timer. Once I found a good OEM starter from the salvage yard and put it on, problem solved.