VPC Gateway Setup problem

I followed this tutorial to set up a gateway server and VPC-only backend server (I’ll refer to them as GW and BE for brevity’s sake). However, after removing the public IP from the netplan file in the last step of the BE configuration guide, the backend server cannot access the internet at all. For whatever reason it seems the backend server is not successfully using the GW as a proxy to access the web. Whenever I try to ping a site (i.e. google.com) from the BE it gives me the error: “Temporary failure in name resolution.”

I know some people have had trouble getting this configuration to work because UFW was blocking routing requests on the GW server, but the results are the same for me even if I disable UFW on both servers. I know the GW and BE are connected in the network because I can ping the BE via its private IP from the GW. Any help with why this isn’t working would be greatly appreciated. I also don’t know how to troubleshoot where in the rerouting process the problem is occurring, so tips in that vein would be useful as well.