Maybe the DLC didn't go to the correct folder. When you open the main menu, there should be a box in the corner called "DLC Info". Does that show the Wedding DLC as being installed?
Thank you so much for sharing that image, that's a big help! I think I see the problem. It looks like the Wedding DLC is still in its zipped format, which is why it's not showing up as installed. Try extracting it to the same folder and see if that works.
