First, some computers have a switch on the side that shuts the WiFi on and off. Make sure that switch is in the proper position, if it has it.

Next, make sure Wifi is enabled in the Network Connections tab.

Next thing I would do is make sure the computer is plugged in (not on battery power), shut it down properly, and restart it.

After that, I would connect it to the internet via hard line and make sure I've got all the updates, including driver specific updates (Windows automatic updater often won't give you those). A BIOS update might also be in order. Then I would properly restart it again.

If it still isn't working, and I can't find any other known fixes by searching the web, then my guess is it's a hardware problem and you might need to talk to Acer.