I installed TKL appliance (Redmine) on VirtualBox at office.

We have Fortigate firewall with VPN configured.

Access to appliance works perfectly inside the office LAN but fails when accessed from outside using VPN. Other appliances that do not use TKL are accessed from inside and outside firewall. I tried to look into TKL firewall (default configuration) but did not find what's block the network traffic. 

Can you please help?