Pam Radius - Kerio Active Sync

I proceeded with configuring pam_radius + Windows NPS on Centos 7 for Kerio Connect using DUO as the proxy Gateway . I am constantly being prompted to authenticate for DUO when I configure Outlook on (Android/IPhone) using Active Sync.

~Webmail / Outlooks works fine with no issue.
~I configured OpenVPN/Windows NPS with Duo and it works with no issues.