non manifold edges hfss
Actually, I'm not sure whether I'm right.
But I was told that; if you're confident that you've drawn your structure in correctly, and you still get the above-mentioned error message. You can high-light the troublesome objects and do the HFSS option called "Heal Objects".
Try it! It might work, you'll never know! By the way, I think the message sometimes pop up when you have 2D objects sharing a common edge, or a loop within a loop. Hope these help.
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