need Help (pop up SSO authentiction) on my webmail/owa securing with FortiWeb

Dear all,

i need some advice.

I'm Newbe in Fortiweb implementation, i had config Fortiweb to secure webmail/owa application.

i had follow the guide below,

https://docs.fortinet.com/document/fortiweb/6.3.9/securing-owa-and-activesync-with-fortiweb/579598/overview.

for the first time i can access the application (webmail/owa), but suddenly after few minutes came out SSO pop up like image at attachment.

please give me an advice ti solve this problem.

regard

yakin