Answer:
The wireless (Wi-Fi) antenna connector is not connected properly.
Step-by-step explanation:
In this scenario, you have verified that all your wireless settings on your network device such as a router, access point, switch and laptop are correct. Thus, what is most likely the problem if your laptop has recently been serviced and wireless connectivity has stopped working is that, the wireless (Wi-Fi) antenna connector is not connected properly.
A wireless (Wi-Fi) antenna connector refers to a coaxial cable connector installed on a laptop so as to enable it to receive nearby radio frequency (RF) signals in order to successfully establish a network connection. Thus, when it is not installed properly, wireless connection on the laptop would not be available.