There are 5 solutions :
1) Go to Network & Internet Setting > Airplane Mode > Slide on the "WI-FI". If cannot slide on, then :

2) You need to press the "wifi" switch button on keyboard, if there is no wifi button on keyboard, then you need to download software to switch Wifi on. Go to your laptop brand website download Network Connection manager. Example if HP brand, then go download HP Connection Manager. Open it > Preference > Device Power > Check both option as picture below :

3)After Done Step 2, then restart computer. Then try to do step 1 again, hope success slide on on "WI-FI" for this time. If cannot slide on, then :

4) Window Search and open "Windows Mobilility Center" > swith on WIFI.