If your credit card terminal is disconnected from WIFI and shows 'Network Disconnected', do follow the steps below.
Press '9' and then the green O button.
Key in the PIN: 2580.
Go to Network > WIFI > Select your WIFI network to connect again.
If the above steps did not work and you do not see a WIFI icon on the top right of the screen:
Select the blue 'i' icon next to your WIFI network and select the trash bin icon to forget your network.
Select the '+' icon again to scan for WIFI networks, select your WIFI network and key in your password to reconnect again.