You may receive this error when trying to log in to the Deployment Manager web interface:

 A required anti-forgery token was not supplied or was invalid

The causes for this error may be:

• Cookies are disabled in your web browser.

  For information on how to enable cookies, refer to your web browser's documentation:
  Manage your cookies and site data (Chrome documentation)
  How to manage cookies in Internet Explorer 9 (Internet Explorer documentation)
  Enable and disable cookies (Firefox documentation)

• Session cookies have expired.
  This can happen if you leave the Deployment Manager web interface on the Login page for several hours before trying to log in. If your session cookies have expired, you need to refresh the Deployment Manager Login page before you can log in.