SSL VPN Portal link to Exchange OWA not working

Hello,

I configured SSL VPN Portal with link to Exchange OWA (https). Sometimes this link works sometimes not. Example of logs on fortianalyzer Event->VPN

Blocked traffic

Action: ssl-web-deny

destination host: mail.domain.com

group: VPN

IPSec Remote IP: 1.1.1.1 (some public IP)

Log description: SSL VPN deny

Message: SSL web application blocked

Reason: https

Sub type: vpn

Tunnel type: ssl-vpn

User: some_username

Allowed traffic

Action: ssl-web-pass

destination host: mail.domain.com

group: VPN

IPSec Remote IP: 1.1.1.1 (some public IP)

Log description: SSL VPN pass

Message: SSL web application activated

Reason: https

Sub type: vpn

Tunnel type: ssl-vpn

User: some_username

I have this 2 logs for the same user in the same day but in different hour.

What rule or security setting can block this traffic?

regards

kbar44