I enabled third-party cookies in my browser, but I am still getting an error message to enable third party cookies! Why?

When this happens it is usually the result of a privacy extension or ad blocker. You'll just need to add b4g.baydin.com and mail.google.com to the extension's trusted (i.e. accepted, whitelist, etc.) list. Then reload Gmail and give it another try. 

If the issue persists, please email support@baydin.com.