From what I've been looking at you
can play a card against Omega Barrier
even though you know it would fail. That sort of flies in the face of "you can't play a card for no effect" ruling you see in The Compendium, but I guess this is different because of the circumstances.
Compendium says
"You cannot play a card if it is public knowledge that it will have no game effect. Paying a cost does not satisfy the requirement that the card has a game effect. (Jan 31, 2008 PUI Rules Team; Mar 12, 2009 PUI Rules Team)"— and it says similar quotes a number of times throughout.
But then we get this for a precedence:
Q. Can I play Eneporter to try and fail to move a Special Energy onto a Pyroar that is protected by its "Unnerve" Ability, or would I not be able to play Eneporter at all?
A. The fact that its effect will be blocked by another effect such as Unnerve
does not prevent an Item or Supporter card from being played. For example, your opponent may play Eneporter to try moving a Special Energy and Pyroar is a valid target, but Unnerve blocks the effect even though Eneporter was played. Playing a card for no effect happens when the game state itself prevents any effect from taking place and in that case the card would not be played, but that is not what this example is referring to. (Forbidden Light FAQ; May 3, 2018 TPCi Rules Team)
So in this regard the card can be played but it just gets blocked by an effect of something. Not like you were trying to play a card when no effect would've happened in the first place— Omega Barrier puts a condition out there that changes things.