Alisha Gambhir writes in, noting that her MacBook Pro suddenly reported that it had no Wi-Fi hardware installed. This is odd because, as you know, all Mac laptops (and nearly every Mac made for several years) includes a Wi-Fi adapter.
There are two ways you can wind up with an x in the Wi-Fi menu’s icon. One is what’s happened to Alisha and other folks who have posted about this problem over a few years; the other is when the adapter has been disabled via the Network system preferences pane. If you click the Wi-Fi icon and the dropdown menu reads “Wi-Fi: Not Configured” then the adapter has been disabled.
If that’s the case, you can re-enable it:
Launch System Preferences and click Network.
Select the Wi-Fi adapter in the list at left. It will be grayed out and have the label Inactive beneath it.
From the gear menu, select Make Service Active.
The x will disappear from inside the Wi-Fi fan, and your computer will scan for networks or connect to a known one.
If hardware is the issue, the Wi-Fi drop-down menu will read “Wi-Fi: No Hardware Installed”. That’s either a low-level configuration issue or a hardware problem. You can try to clear the hardware state by resetting the non-volatile memory (NVRAM) or the System Management Controller (SMC). In forums, many users were able to solve the problem by resetting one or other of these.
But if resetting those two system states doesn’t bring Wi-Fi back, it’s time to hit the shop. If your Mac remains under warranty, keep details of your testing handy and call for a repair. If it’s out of warranty, you can avoid an expensive motherboard or module repair by getting a third-party Wi-Fi USB dongle, like the Edimax AC1200, which comes with drivers from the maker for OS X and macOS through Sierra.
Updated: The Edimax adapter’s maker added a Sierra driver.
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