Not knowing the operating system and service pack makes everything guesswork, but try right-clicking the network icon by the clock and selecting Diagnose and Repair.
Technical Support is free and available by phone if necessary and linked under Useful Links at the top of this page.
Please provide us screen shot of DNS settings of your active network.
Open Network & Sharing Center: Click on the icon of your internet connection on your task bar. At the bottom should be the words "Open Network and Sharing Center"; click on them.
Click on "Change Adapter Settings" on the left-hand list of topics.
This will direct you to a page where you will see your LAN (wired) connection and your wireless connections.
Right click on the network connection you are using.
Scroll down to and click on “Properties". If prompted for an administrator password, provide one.
A new window will pop up. Double-click on "Internet Protocol Version 4 (TCP/IPv4)"
Another new window pops up. Look at the lower grouping of grayed-out boxes. "Use the following DNS server addresses:”
Take a screenshot of this window and reply us, it would look similar to one I am attaching below