3 weeks post-op. Is my belly button dead? (Photo)

The photo is not very good to tell and be sure your BB is necrotic or not, BUT I truly consider based on what I can see your belly button is OK and will heal shortly. BB heals normally very good, no matter what, even if it is infected,  necrotic or dehiscence. Be encouraged. Your BB will be OKDr. Cárdenas 

Thank you very much for this question and the attached pictures. You seem to be suffering from a minor wound dehiscence. The inside Navel howeverLooks viable. My advice is to keep it clean with peroxide and cover it with a sterile gauze. Let your plastic surgeon check you regularly. And follow his advice. Have a wonderful rest of the day

many thanks for the question and pictures.
It appears that your belly-button is viable. I would advise that you keep under close review with your surgeon to keep an eye on your scaring and to intervene early should signs of hypertrophy or keloid scarring become evident.
I wish you all the best.
Marcus

Thank you for your question. It’s difficult to determine based on the photo, but the belly button appears to be viable. If you are concerned I recommend seeing your plastic surgeon for a follow up. Best of luck with your recovery.