If you have already added balance to your LIVE account, and you suddenly notice that your wallet balance displays zero then most probably this means your account is on TEST MODE.
You will notice this because the left side panel will show in aqua green colour and the switch will state "Test mode ON".
See below picture:
Go ahead and Switch Test Mode to Off and your LIVE balance will be seen again.
If you are still having problems, get in touch with our Customer Success team. We will be more than glad to help!