Fortinet VPN client won't work with my Archer VR900
I have a weird problem with my VR900. Everything works great apart from my work VPN software that runs on a laptop. It uses a Fortinet VPN client and it connects fine but can't then get to anywhere or transfer any data. I have tried disabling the SPI on the router, turning on and off all the IPSEC forwarding stuff and even putting the laptop IP address in the DMZ and it still won't work. It works fine if I plug in my old router or if i connect on 4G with my mobile.
Its an SSL-based VPN client.
Is there anything else I can try? I am going to have to ditch the router if I can't find a resolution to this weirdness.