I have not been able to start my car

Just so I am clear, the issue stated when you put the crank sensor in that you bought online? If that is the case then yes. That is most likely the cause. I attached the part number from the OEM and I would suggest getting one of those and see what happens.

A crank sensor will prevent the start because it is needed to time the injectors and plugs.

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

The cam sensor and crank sensor are different but it appears they may be the same actual sensor or the same part number.

Here is a common parts website that should help. Screen shots below of all this info and of the website. One of the cam sensor and the other of the crank sensor.

https://www.rockauto.com/en/catalog/nissan,2006,altima,2.5l+l4,1432235,ignition,crankshaft+position+sensor,7196

Well thank you. I appreciate that.

I don't think they were deceiving you, I think they just didn't explain things very well. I have never seen a vehicle with 2 crank sensors. Which means they more than likely felt you needed two sensors and maybe they were the crank and cam sensor. Did they give you an estimate with this laid out?

As for what sensor, the OEM is the best because it was produced specifically for this vehicle from the original specifications made by the designers. All aftermarket sensors are called recastings. Meaning they took the original and made a copy of it which means they could get something wrong. Think of it like trying to copy a well known painting. It may look the same but it is not the original.

All this to say, just because it is not an OEM part, doesn't mean it is no good. I use aftermarket parts all the time and have good luck and not so good luck with them. Unfortunately, there is no guarantee with any of the parts you buy.

The way I look at it is I always evaluate cost vs, easy of replacement. If I have to take the engine apart to replace the sensor then I only want to do it once so I get the best quality part I can. However, if it is easy to replace, I will get the cheapest because if it fails I just swap it out.

As for Rock Auto, the standard part is considered an OEM replacement. The economy is normally the cheaper parts.

Hopefully I answered all your questions.

Yeah. That is parts and labor but still pretty pricey. Fingers are crossed. Let us know what happens. Thanks