Why is the router not pinging?

Question

Computer networks

Unable to ping the router and devices behind it from the server.
How to properly configure Internet access for devices connected to the router, as well as connect to them from the server?
Here is an approximate network diagram:

Answer 1

You most likely have an Ubuntu server plugged into the router's WAN port. Therefore, from the point of view of the router, Ubuntu is an external system, and by default, control from outside is blocked for such devices, incl. and pings etc.
In addition, a route to the network 192.168.0.0/24 must be registered on Ubuntu (route print).

Answer 2

Counter questions:
1) At what address are you trying to ping the router (.1.2 or .0.1)?
If by .0.1, then it will not work due to NAT and, most likely, the lack of routes. However, for the same reason, pings for the router will not work either.
2) Why do you need this?
It’s not a question for the sake of a holivar, but it’s just not clear why you are using the WAN port of the router? Maybe it's easier to plug Ubuntu Server into the LAN and then everything will work by itself?