What could make a bmw not start?

Spraying starter fluid and it running for a split second tells me it is fuel related. Do you hear the fuel pump prime when you turn the key?

I hear the fuel pump and I did a test on something in the engine bay and I am getting fuel, checked the fuse for the fuel pump anyways and still nothing

There’s a secondary jet pump that you might want to have checked. I replaced the fuel pump and thermostat in mine and it would not start. Turns out that the sending unit wires were bad and then some reprogramming was done and that did it. Hope that helps.