This is a User-to-User forum. You are not speaking to Apple here, just fellow users like you.
Many WiFi routers test against Windows and do not always play nice with Apple products. Make sure you have the latest firmware updates for your WiFi router. Check with your WiFi router vendor.
Try the following on your Mac:
System Preferences -> Network -> Advanced -> Wi-Fi
Is "Remember networks this computer has joined" checked?
Is your WiFi network in the list of "Preferred Networks"?
Try selecting your network in the "Preferred Networks" list and deleting it via the [-] (minus) button. That will cause the Mac to create a new entry.
Under the System Preferences -> Network -> Advanced -> TCP/IP tab try the following
Give your Mac a "DHCP Client ID". Make it simple, such as "MyMacbookPro", it does not matter, as long as you do not make it complex. Many WiFi routers will remember a device based on the DHCP Client ID, and re-issue the same IP address.
Try "Configure IPv6 to "Link-local only"
I am experiencing the same issue with my new 2013 (late) 13 inch MacBook Pro. BobHarris- This is not a router/connection issue. Everytime I turn mycomputer on after it wasshut down, I am unable to connect to wifi and my wifi logo has a big X on it. If I scroll over it it says "No Hardware Installed" or something to that measure. If I restart the computer (Restart- NOT shutdown) it fixes the issue. But then again without fail, once I reboot from a complete shutdown- same issue.
Since my product is barely 3 days old- I should be able to return it for a refund/ and or exchange it for a brand new replacement, right?