What is the status of the WLAN network adapter as shown in Device Manager?
Does it state that "This device is working properly"?
Go to Device Manager > Network Adapters > right click on the WLAN adapter entry > Properties > General tab > Device status box.
If it shows that it is working OK does the laptop show any available WiFi networks in the WiFi list?
If not try using the laptop as close as possible to your WiFi router i.e. <20cm, and check if it detects the network. If it does then it may be a loose or disconnected antenna problem.
See Step.36 of the ifixit Microsoft Surface Laptop 3 13.5" Motherboard Replacement guide for the location of the antenna connection on the motherboard.