2006 Lexus IS wont start

There are a number of things that will cause this, but we need to start with fuel pressure to find out if we blew a fuse into the fuel pump.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Basically, the fact that this is a diesel means that we have an issue with fuel or compression and if it was running prior to servicing it then compression is not the cause.

This means we need to focus on fuel. You can also use ether in the intake and see if the engine starts.

Lastly, what exactly was the service that you performed? Did you just change the oil, or did you do something with the fuel system?

Let's start with this info and go from there.

Thanks