|Because you have it configured for IPv6.|
If it were me, I'd disable IPv6 on that PC as it could be part of the connection issue that computer is having. In fact, I'd disable IPv6 on all internal PC's making sure beforehand they IPv4 settings on them are properly configured. Disabling IPv6 is as simple as unchecking the "Internet Protocol Version 6 (TCP/IPv6)" box in the properties for the network interface
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.