Mesh WiFi 6 Router(MR60) & L2TP VPN via Synology

Just bought and installed the Mesh WiFi 6 Router(MR60) and am trying to configure the port forwarding for L2TP VPN service to my Synology Server. I believe I have the 3 ports configured correctly (500, 1701, and 4500); however, my remote device still does not want to connect. I have to believe the router supports passing the L2TP protocols through...any ideas?

UPDATE: Played around with some more settings and finally got it to work...the Nighthawk router sits behind my ATT Modem/Router that I configured as a Passthrough. However, I suspect that because the devices that sit behind the Nighthawk router technically reside on a different subnet, I had to redefine the port forwarding rules on the ATT router to point to the Nighthawk router - so I guess it essentially gets forwarded twice. Looks like everything is back to working order.