My dog passed away yesterday, and I’m not upset as I thought I would be. Is this normal?

Everyone handles grief differently. Don't start thinking there is something wrong with you because there isn't. One day it will come and you'll know it. It might be when you see a touching dog food commercial or go to a shopping center and see some puppies in the front of a pet shop. Believe me, you're reaction is not that unusual. Just crying and carrying on doesn't act as some kind of measurement of how much you loved the dog.

I have no idea - this has never been my experience.

Ive had death happen so much that I just go numb.

Could you be numb? Being numb is still distress.

"Why can’t I express my emotions?" You can't express something you don't feel. This is not rocket science.

David B. might be right, but in some cases, if the dog lived a good long life and the death was not unexpected, you may have already come to some acceptance (beforehand) or been relieved she did not linger and suffer.

When my father died it was very much expected, and I was relieved (even grateful). He was suffering..... and so was my mother (who would NOT leave his bedside for days on end.) Caring for him, even with hospice care, nearly killed her. She would hardly eat during that period, and had lost 15 pounds she could NOT afford.