I work from home and connect my work laptop to a forticlient VPN to a server at my place of employment in the same city.  The VPN session connects, but applications fail repeatedly.  I ran a speed test when connected to this VPN and I only get a downstream speed, there is nothing for the upstream speed.  When I disconnect from the VPN and run a speed test I get normal downstream/upstream speeds.

I bought the Deco X55 to replace my older Asus router (which works flawlessly over VPN with default provisioning).  I had to disconnect the Deco and reinstall my Asus router to resume work. I was unable to find anything in the Deco system settings that would make the VPN work.  I hope someone has an answer for this issue, otherwise I will need to return it and find a mesh router system that will work with VPN.

Edit:
I happen to have a TP-Link AC1750 WiFi range extender Model RE450 (US) Ver 2.8 which I used with my Asus router before purchasing the X55.  I connected to that extender and then established my VPN work connection, and ran speed tests. At first, I had downstream/upstream traffic but very slow. After testing again the speeds improved and I was able to open applications at work, but after a short time it stopped working.  Upon running speed tests again, I was getting no upstream traffic, and at times no up/down traffic.  I read several other forum posts where people used the guest network on the X55 to make the VPN connection work. This did not work for me.  Clearly the X55 is blocking traffic to my VPN connection which tells me it is not allowing transparent tunneling.  I have also connected with an ethernet cable to the main router and connected to my work VPN and still having the same issue.  VPN connects, but cannot pass traffic, as tested with speed tests.