Hi @sitiaisyah
Does the Bluetooth work OK?
Try using the phone as close as possible to your home network router i.e. <10cm and check if the WiFi network is detected.
If you can detect and connect to the network then there may be an antenna problem (loose?) with the phone.
Here's an image taken from this teardown [https://www.youtube.com/watch?v=Ve_CgJu8goU|video] showing the antenna connections in the phone..
[image|3187122]
(click on image)
If it still doesn't detect the WiFi network and if the BT doesn't work either there may be a problem with the WiFi/BT IC on the systemboard.