I got my ascendant raisins from the speaker (giving him 25 motes of light), then went to zavala... he doesn't have the option to take them. And before someone asks, yes, I bought rise of iron.
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TMF1979's suggestion will help identify the issue, but before you go through the trouble, are you sure II are talking to The right vendor? Some others have posted videos and it turned out they were talking Shaxx instead of zavala.