To give another deviant a direct link to this FAQ answer, use the following code in your comment or forum post:
Why did my order fail due to connecting from a High Risk location?
Due to the wide range of international purchases received, deviantART employs certain requirements on transaction security which are sometimes quite strict. This applies to certain world locations where we have experienced a high amount of fraudulent activity in the past. If you are connecting from one of these locations then it is probable that your purchase will not succeed.
These selections are based simply on past attempts to transact massive amounts of fraudulent transactions on stolen credit cards from such locations, and nothing more.
If you are experiencing this, unfortunately there is nothing we are allowed to do in order to change the outcome of this for you. We can only suggest you try connecting from a different location which may not be tagged as a High Risk area, or to try signing up for Verified by Visa or MasterCard's equivalent Secure Code.