Is the problem people using unreleased cards in multiplayer, if so, you need to make sure to only join lobbies with the same version number as you.
Viewing post in Weiss Schwarz Simulator V0.5.3 comments
When playing in the same lobby with the same version, this issue occurs. For example, using cards like the recently released 5HY can result in the display of blank cards. However, the behavior of the cards accurately executes the effects of the new card. If this is due to my lack of understanding, I apologize. Is there always a way to add the latest cards?