Couldn´t access Dark Sovereign event

So, the event was/is scheduled on the 20th every month, but  yesterday in my Journey Guide I had the whole day a timer with the description "Starts in XX.XX", but then it disappeared and now I hear from my guildmates, that the event is already over (unfortunately I have no screen).

I had no pop-up, no nothing in the event card or in the journey guide, my question is where can I find the event next month, so I can finally get my Leviathan?

(I already bought ca. 3 packs of shards before the event, could this broke it to me?)

Thank you.