It sounds like the wifi driver is missing. Go to Device Manager and look for Network adapters. Do you see Unknown Device in the Network adapters section? If so, right click on Unknown Devive and click on Properties. A new window will pop up. Click on the Details tab near to top. You will see Property, under Property, click the down arrow to the right and choose Hardware Ids. Under Value, you will see a list of letters and numbers. Right click the first line in the list and choose Copy.
Next go to Google, right click in the search bar and click Paste. Do a search for that first item in the list. That should tell you the make and model of your wifi adapter.
Next go to Acer's website and look up the model number of your computer. Look for drivers, and you should see the wifi driver for your computer. Download the wifi driver and install it.
The reason I had you look up the make and model first is because sometimes they will list two or three wifi adapters for the same model computer. This way you will know which one to download.