@Vintage-MR600 

Hi

1. Check and ensure the internet line or ISP modem is stable, bypassing the TP-Link router. Connect the PC directly to the ISP modem (or internet cable from the wall), test and monitor the internet connectivity, and ensure you have a stable connection.

2. If the modem internet is stable, please connect the router back to the network, and ensure the Ethernet cable going from the ISP modem to the WAN port of the router is securely connected. Try with another Cat5e/6 cable or change the port of your ISP modem, to where you're connecting the TP-Link router (if possible).

3. Check and ensure the router firmware is up-to-date.

  @Joseph-TP 

Yes my Modem is updated, the problem will be fix if I restart my modem then when no one using the wifi or lets say the lan for a few hours, the internet will be gone so I have to restart the modem again.

the problem is only caused by the modem because I tested the Starlink Wifi and there is no problem, but yea I need extra lan port so I have to bypass mode my starlink.