Exchange Outlook email

I've had my work email on my phone for years. All of a sudden I stopped getting emails on it. I tried deleting the account and re-adding it. WHen i try adding the account back the web page to "sign in" pops up and them immediately disappears not allowing me to sign in to my Microsoft exchange email. I then get "Unable to verify your account", and can't add it back. Any advice? Restarting the iPhone doesn't help.