Sigma EF-530 DG ST Flash wont trigger

[Dopi]

So I got a Sigma EF-530 DG ST flash on my canon EOD 400D.
It's turned on and it sits right where it should.
So my problem is, the flash wont trigger when I take a photo. Everything else about the flash seems fine, except it wont trigger when I take a photo.
Besides, it is flashing when im pressing the "test" button.

Anyone knows whats wrong? How I can fix it?
I need my flash tomorrow, so if anyone could answer ASAP, i would really appriciate it.