Have you tried to change the default ISP DNS to something different and see if that can resolve the issue: Reboot the router after making this change.

@BigZ Here's the difference (old router): Your old router is receiving public IP address, which is the correct behavior. This is AX10: Here, you're receiving a private IP address, which is different...

Yes, you got it right. Open the 443 port on the ISP router to the C6(8080) IP address and test with public IP on port 8080 in the browser.

@GA_Polo OK. Lets do the configuration change only for one C6 for example - first one - management port 8080 (if you don't mind, or other at your choice). Assure yourself that the remote access in...

Is the topology like this: <Media Converter>=><Switch>=>AX10=><your local network> You have a double NAT in your network. Once before the AX10 and then again in the AX10. Are your WAN/Internet port...

My question was - do you have any ISP device (modem/router) to which you connect the AX10 ? If yes, then what is it ?