I would get the details from user like how often does this problem occur or when did this problem occur and will solve it accordingly. If the user is clueless then i will first check the hardware and see if everything is fine and no hardware needs to be fixed or replaced then I will check if there is no problem with drivers and there is no need to update or replace network drivers if it's okay Then i will check ip configuration in cmd or terminal depending on OS if there is no ip showing i would reset the adapter and try again and if the ip shows then i will check if the ipv4 or ipv6 configuration is according to parent network i.e static or dhcp and see if the default gateway is correct and if there are private dns servers then they are entered there if everything is fine and still internet does not work i will use troubleshooter on the adapter because sometimes computer knows better