I have Denny's rewards, and I wanted to get my free breakfast on my birthday, but it doesn't recognize my password, and says it will email me in 5 days with a new email, but my birthday is in 2 days!

Tell the cashier

I wouldn't worry. Show your texted concern to a Mgr at Denny's, I'm sure they'll honor the b-day freebie. Wait the 5 days first.

Same happened to me i just asked nicely and showed it actually was my birthday

I would call the manager and ask explain the situation and see what they can do for you.