I could attack but play no cards

I was able to just attack, but I couldn't play any cards that I had in my hand. This was especially frustrating because I could've won 3 turns in a row, but because I was unable to play the card. There was also a blanked-out card in my deck, that I drew into that turn and showed up in my hand as the backside of a physical Pokémon card. Which was when I was unable to play any more cards.