Why my Samsung phone is not connecting to Wi-Fi?
Check if the router is working properly. Make sure that it's powered on, connected to the Internet, and that your phone is within the router's Wi-Fi range. In addition, if too many devices are connected to one router, the Wi-Fi may not be detected. Note: The router display may vary from device to device.
Why is my phone not connecting to Wi-Fi but other devices are?
Check to make sure that your phone is connected to the correct network, and that the network's settings are correct. You may also want to try forgetting the network and reconnecting to it, as well as checking for any updates to your phone's firmware.
How do I reset my Wi-Fi on my Samsung phone?
How to reset network settings on your Android phone or tablet