I’m using an OpenWRT-based router.
My X1C gave me errors that it wasn’t connected to the network.
It passed the network test.
I could log out and back into the router.
I was able to download new firmware.
I tried the 20/40 changes and several others, but nothing worked.
I knew there was some type of connection, but it was just not fully functional.
It ended up being a DNS issue.
I had my router set to use Google as the DNS provider. When I changed this to Cloudflare, it instantly started working. Changed it back to Google, and it failed again. I now have Cloudflare as my upstream DNS and have not had issues.