Please perform the below mentioned steps to resolve the issue:
1) Forget the Network:-Go to apps screen >Settings >Connections > Wi-Fi >Wi-Fi network >Tap and hold the Wi-Fi network that you're having trouble with until the menu allows you to select Forget Network.
2) Reset Network Settings:- Go to apps screen >Settings >General Management >Reset >Reset Network Setting.
3) Restart the Router and Mobile Device
4) Kindly check and disable the Airplane/Flight Mode on your device.
For further assistance, register your concern in Samsung Members Application (Open Samsung Members Application > click on “+“icon > send feedback > error report/ask questions).
