Which listing is it, we'll be happy to take a look and check to see if the GSP has been applied to your listing and, if it has, that Singapore is an available shipping country.
Just a heads up - you cannot use the Nike brand logo as an avatar unless you are Nike or have their permission - it's a copyright breach and you're leaving yourself open to legal action from US lawyers (we see a few of these).
You also need to be trading on a business account. At the moment your buyers are being charged an extra Buyer Protection fee and you're limited tom using eBay's Simple Delivery.
To correctly register as a business seller simply go to your Personal Information in your account and to the right of Account Type, which will be showing as 'Individual' you'll see an Edit option.
https://accountsettings.ebay.co.uk/profile
This doesn't affect your feedback profile or any current listings, it merely upgrades your account so that you're compliant with current consumer and eBay policy.
