Dark Magic Curtain didn't work for me when Arkana was using it, I had Dark magician girl on my hand, and dark magician in my deck, I could not summon any of them!!
Yeah, I’ve had many problems where this card won’t activate and have lost many games due to this issue. Right when my turn would begin I would try to use this card and the game wouldn’t let me. I’ve email konami many times about this and they only response I’ve got was an automated email saying it’ll take them a couple weeks to email me back. That shows me that they don’t really care.
If you normal summon a monster before using it you can’t use it for the rest of the turn, “you can’t summon a monster the turn you use this card (but you can set)” meaning you must set a monster if you want to use it