Whenever I try to tap a creature ie llanowar elves or an artifact for mana, the game doesnt allow me to do so. It seems like the game doesnt recognize the permanent being able to tap for mana or activate its abilities.
It doesnt happen every game, nor does it happen every turn within a game. For example I would be able to tap a llanowar eleves for mana on turn 2, but then on turn 3 it seems the crature lost its ability.