Since the update with the new set there seems an issue with Omniscience. Whenever my opponent or me played Omniscience in TotP cards would fill up/cost 0. But instead of being played, the turn would end right away.
The issue doesn’t show up with Hazoreths Undying Fury where cards also cost 0 mana.
I have noticed this as well as of the newest release. Omni shows all of the cards in hand as playable, but doesn’t allow any of them to be played until the following turn.
After casting Omniscience if you still have another card that was already full mana and ready to cast before casting the Omniscience then your cards will keep casting without having to wait a turn.
There’s a very similar problem with Colors of Magic at the moment, and I think it could be a result of the same bug: the event supports in CoM, just like Omni, reduce the costs of cards… when a card’s cost hits 0, it’s supposed to cast, but playing CoM today I often had to wait an additional turn for them to cast.