04 jetta tdi BEW won't start when engine is cold

I have a 04 vw jetta tdi bew. About 6 months ago I tried to start it and it would turn over but would not start and the glow plug light would flash. I changed the lift pump in the tank, fuel filter, tandum pump on the cam, injectors, crank and cam sensors. I also checked the glow plugs and glow plug harness and all was good, even though I live in Louisiana and rarely need the assistance og the glow plugs.
About a month ago, I put the original crank sensor back on because the one I bought did not look like the original and it cranked. It did so for about 3 weeks, would crank right up, then last week it was back to its old ways. It does start when I use starting fluid, and I know its not good for the engine. If I start it and run it till it gets to normal operating temperature then kill the engine it will start right up as long as the engine has warmed up. When it does run, it runs great.
Last week I was driving, felt the engine miss upon acceleration, when I parked and let the car cool is when it was back to no start, after 3 weeks of starting like a champ.
I don't know what else to do. I need some TDI wisdom.

Just a guess, but perhaps the lift pump in the tank has failed. You should be able to hear it when you turn the key on, if you really listen. Lift the lower part of the back seat up and remove the little access cover and you should for sure hear it.

The original lift pump was out, I believe that may habe been one of the original causes for the no start but I did replace it with a new one. I am getting fuel through the filter and to the engine.

Did you scan for codes while the glow plug light was flashing?

Yes I scaned for codes and they were for the crank sensor and the MAP sensor. I changed the crank, cleared the codes and the MAP never appeared again.