I've had trouble with one particular player at the local game shop where I play. He's normally a nice guy, but he gets easily confused with the rules of his codex. Of course, there's a good reason for this: English isn't his first language. He's Russian.
He can speak fine, albeit with a thick accent, but he has trouble with the subtleties of English, making interpreting his codex tough, especially since it's the Witch Hunters codex, which has some strange and vague rules to begin with.
Someone older than 12 and whose main language is English, however, has no excuse. Tell them to read the codex from start to finish once more, and then try again.
He can speak fine, albeit with a thick accent, but he has trouble with the subtleties of English, making interpreting his codex tough, especially since it's the Witch Hunters codex, which has some strange and vague rules to begin with.
Someone older than 12 and whose main language is English, however, has no excuse. Tell them to read the codex from start to finish once more, and then try again.