LM1200 won't connect to router

I have to say, the manual for this device is pretty useless. There are zero instructions on how to set up failover, explaining the failover settings, or even just explaining how to connect to a network generally. After some experimentation I was able to get it to work with my google nest router, which is connected to my switch on my home network. I set it to bridge mode and turned on failover, then plugged the WAN side to my modem and the LAN side to my google nest router. And it works.

However I cannot get it to work with my synology router on my work network whether in bridge mode or router mode. I plug the LAN side on the LM1200 into the WAN plug on the router and it does NOT have internet access.

Even if I didn't want to use failover, I cannot figure out any way to connect it to my office network. It won't work with my switch even when in router mode. And I do want to use failover that's why I bought this thing.  Firmware is up to date, and it does work when directly plugged into a single PC, it just won't work when plugged into my synology router or switch. Does anyone have any ideas?