The birthday bells don't always work, but this is the same for everyone, so we don't reimburse for them. See this old post:
you should disable it then honestly, it's hardly fair one user gets them and another doesn't, especially since they're going out their way to ask for them. fair enough you can't manually go through every user but i don't see anything wrong with kate asking (sry for being the party pooper that says we should get rid of them but we all love a fair time)