ubuntu desktop can't reach most websites

I’ve just installed Ubuntu on an a reconditioned desktop, and am using an Ethernet to Wireless converter (plugs into Ehternet port and then that connects to my ATT wireless home router). I am not sure if the last network detail matters but for some reason most of the websites that I try to access from Google search are not accessable. I can get to major websites but none of the others like stack overflow etc cannot be reached. Do you know why this is the case? I’ve used ubuntu on another laptop and have never experienced antying like this.