@Stefan4 From these logs can be seen that your PPPoE session to your ISP disconnects and then reconnects again. Given that you've replaced the ethernet cable already, it's reasonable to call your ISP...

@sajidmkm When pressing the reset button you should feel/hear a click. If the router doesn't reset for 10 seconds while pressing this button then device may have another issue. Usually TL-WR850N is...

@ktatar156 It seems like you need to configure port forwarding on your Archer A8 - details.

@Sal123 Can you describe your network infrastructure. What are the devices that you have in your LAN. After a successful reset you can follow these guides on how to setup your AX10 or AX55. Here's...

@akbarf858 Here's a guide on how to change your wireless password.

@Sal123 Do you have any other device in your network like ISP modem/router with DHCP enabled ? Make sure that you didn't enable Acceess Control Whitelist or IP&MAC Binding on your TP-Link router....