I gave Ysolda her Mammoth Tusk and she tells me it's a fine day when I'm around, but when I wear an Amulet of Mara, I don't get any marriage dialogue. Could there be some conflicting quest? (I have not done Sanguine's quest.)

I have both Hearthfire and Dawnguard installed.

Have you spoken to Maramal first?

Ah, that's right. Forgot. Thanks.