I usually make sure my available balance is $0 and then i'll select the Add On and try to apply it. When I do that it will ask me to enter a voucher or Credit Card for the amount required and after I do that It gets applied to my account. Hope this h...
I usually will choose my add on and it will say that you don't have the available balance but it will give you the option to top up and on the top up page will say how much is required (the add on price). Put in the voucher or credit card and confirm...
Make sure on the device that you are using to check the website that your date and time setting are correct. Sometimes when it's not correct it will give you errors that the webpage is not secure and won't connect.
