You replaced all the caps? Also, the glass fuse is soldered in right next to the AC input, you verified it isn’t blown?
There will be a few zener diodes near the switching transistor (IRF831 or similar). You need to test all of them…and the transistor. When switching power supplies completely die they usually go out with great fanfare! That is why I always say it's best to recap and reflow them before they go out. They also use an IC on many of the more modern switch mode power supplies, those are known to go out. I don’t recognize that as a factory Sigma PS, is there any indication it was already changed?
Chris