Won't start, good battery, starter and fuses. Light but no crank.

As suggested,check the battery pos. and gnd connections and I hear that the ignition switch on these cars can cause multiple electrical issues.just a thought

Did major collision for 20years and have seen this. How old is the battery? There is a space between the plates in the battery and the bottom where debris from the plate collects with age and with an impact it can shift and get into the plates and cause a internal short and even jumping it wont work. How was the battery tested and what is the voltage before trying to start and during?

Run a diagnostic. MY '06 Buick Lacrosse had the same problem and it turned out that the ECM (Engine Control Module) wasn't sending a signal to fire the engine. I also had a misfire in many of the cylinders. I turned the key to accessories for a full second or two then tried cranking it and that WORKED!! At that point I was able to drive the car to the dealer and they replaced the ECM for $715. If that is indeed the problem the Part is about $400 if you want to do it yourself. AES modules said they can program it before they ship it to you.

Batterie cables had to be replaced on my 2006 buick lacross. Everything worked it just wouldn't start.