Hello @ayyop
Thank you for reaching out to us and welcome to the TP-Link community.
Can we confirm who is your ISP? Please check and ensure you can connect back if you plug a computer directly to the ISP provided modem or Ethernet cable and dial up on the computer.
If the above is true, please login to the WR840N web interface page to confirm if there is still a WAN IP address when there is no internet access, try to click Release/Renew or Disconnect/Reconnect on the Internet page to confirm if that restores the connection.
If the Disconnect/Reconnect restores the connection, please save and send us the whole system log on the WR840N, we would like to investigate further. You can email to support.forum@tp-link.com.