1. Reboot the router (disconnect from the power, wait 5-10 seconds and turn it on again) and your device.
2. Make sure that you are trying to connect to your network.
3. Verify the password. Make sure you enter the correct Wi-Fi password.
If you have completed all these steps, but the smartphone does not connect to the Wi-Fi access point and gives an error. So the problem lies in the settings of the router:
1. Encryption. Try changing the encryption type in the settings of your router. Set the parameters to WPA2 (AES).
2. Change the channel. Another solution to this problem may be to change the channel to another.