I would say you may have a faulty card or the antenna wires are not connected inside your laptop.  I would contact the seller pronto.  
I received my refurbished Inspiron 17 5758 on Tuesday. My internet was down and I wasn't able to connect it to my mobile hotspot, but I didn't think much of it. Wednesday my internet was working again, and I can't see ANY wifi networks. I was able to use a wired connection and download a ton of Windows 8.1 updates in the hope that one of those triggered it. Nothing. I updated to Windows 10 and still no wifi. I have tried running troubleshoot and repair. I have downloaded and updated drivers from the website.  Is there something I am missing? My modem/router is N+, I am going to try it at a friend's place tonight, but even if my modem wasn't compatible I should be able to see something.
No wifi on Inspiron 17 5758