Can't place a card, why? Also, can people cheat?

Hey all. Been playing for a few weeks and I have encountered a situation several times that is really confusing me. It feels like people are cheating somehow. I also encountered something tonight that has me confused. I took a screenshot of it but it looks like I can't post screenshots here so I'll explain this after the first issue.

1 - Several times I've encountered people who, when I try to attack, it shows I'll be doing zero damage. When I issue my attack, it appears like there's a shield over the other player's card. I can't see anything in play that would cause that. The example tonight was the other player had a card down. I don't recall the card but nothing on it indicated any sort of damage reduction or anything. They did have the Defiance Band attached to the card but that gives +30 damage for their attacks, not damage reduction from attacks. And only if they have more prize cards than me, but we each still had 6. Other than that, I couldn't see anything that would cause this shield protection. What am I missing? What should I look for next time?

2 - In this second situation, I had two Quaxly's on my bench. One had one water energy attached. I wanted to evolve the card that the water attached but the game would only let me evolve the one without the water attached. Why would that be?

Thanks.