I have a Nissan maxima and I had to replace the harmonic balancer so I got the part and put it on with the new belt and it didn't start so I got a new battery that wasn't it I replaced the fuel pump and filter and both sensor and still nothing

So wait... you just started replacing parts without checking?

It started OK before you put the balancer on, right?

So you put the balancer on and it didn't start and your next step was a battery. Why? Was the battery dead or did you just decide on your own that was the problem?

You then went from a battery to a fuel pump and filters... I wonder how you arrived at this because they won't even give you the same symptoms. Then you replaced 2 sensors... what 2 sensors?

Bottom line, you can't just replace parts without knowing why you're replacing them.
A bad battery would make the car not even crank, or crank real slow.
A bad fuel pump would allow the car to crank normally but not get any fuel and therefore not start.
Bad sensors would cause... well, it depends on what these sensors actually were.
Seems to me like you are just throwing time and money at this car by guessing what's wrong.

Why don't you tell us the story and tell us what it's doing/not doing?