Mac not connecting to ATT router via ethernet-USB converter

Hello,

I've got three different Macs, and only one of them can connect to my ATT router via ethernet:  the Mac with an ethernet port.  The two that cannot connect are using a USB-to-Ethernet converter, and the Mac network configuration tool  indicates "cable unplugged."   Is there something different I need to be doing in these cases where I do not have an ethernet port available?

Any suggestions would be greatly appreciated!

Thanks....Peter