where to start....
400v ballasts are not used as much as 230v, but re probably used on larger type lighting projects such as this instead of 230v
you can test a ballast by measuring resistance from in to out terminal. IIRC, it will be around 5-10 ohms.
best way to test from gound is to get a 1500v lamp & holder, and temp connect to ballast & ignitor at ground level.
also, look at the lamp up high - if you can see black, its probably dead.
also, and very important, if the lamp fails and is not replaced, it will damage ignitor & possibly ballast. so even with new lamp, it still doesnt work