Try the Ignitor (inside the case). It is a small can in (usually) an oval shape about the size of a Zippo lighter. If that's "OK" then the Capacitor (round like a red bull can) could be dead. Either one being bad, it won't ignite. I suspect the Ignitor as these usually go first and they take the brunt (surge) of the start-up electrical load.. Even the best Ballasts need theese parts replaced about every 2-3 years depending on usage and their quality. Some electrical parts simply go for no reason. They are all made as cheap as possible.