Maybe that part of the game can get stuck if you have a Megagross card in your inventory (though you already gave it to Sarah bc you could give her also the Zoodra card afterwards), check if you have it and delete it, that should solve the problem
Sorry I cant understand at which point are you stuck, are you following
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? could you be more specific? which quest are you playing, at which specific point of the quest are you stuck or how you adress the problem? what is the message you get from the NPCs that involved in the mission?