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First, start with a full power cycle of the ISP.
Check that your computer and your ISP are connected to the same LAN.
Check your connections to your LAN: from your ISP to the router and from your computer to the router. Check that the cable with another equipment if possible.
Check that your LAN is using a DHCP server for your ISP first connection.
Check that you have an IP address displayed on your ISP’s Front Panel.
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