Issues can sometimes arise when:

  1. Copying/pasting your info. Try instead manually typing in your email and password.
  2. Make sure your email address is all lowercase.
  3. Using a password helper app. Again try entering your password in manually.
  4. Using a connected keyboard. Try instead using the iPad onscreen keyboard.
  5. Using the TAB key to switch from the email field to the password field. Try tapping into the password field instead. 
If it still doesn't work, contact support via the Submit A Request link at the top of the page.