As an online marketer, you will come to experience situations where you really need to buy a product but your transaction just wont go through despite your card being valid and still active.
This problem is very common with many online merchants and it surprisingly does not affect everyone but a selected few. It can happen to you when you are trying to buy membership into Empowerment Network, Xplocial, The Wealthy Affiliate University, etc...

When this happens, all kind of thoughts are likely to run through your head and when, they overwhelm you, you simply conclude it is probably for the best & you just avoided being scam. There are those few individuals that wont simply quittrying to figure out why the merchant wont simply accept their money. You will probably go mad and start droping all sort if profanity like "just accept my money my money b!tch!!!!" Well, I know Jesse Pinkman would say something along those lines. 

Don't worry and quit just yet until you had tried some of these tips. 

First you will want to establish that the problem is not with your credit card. Call your bank or credit card company and ask them to verify that your card is still active and if they can detect any activity related to declined transactions. Also ask them about the card online purchasing limit just to make sure you stay within. 

You should also check and verify that the credit card information you entered are correct. Then contact your merchant and ask them to check and investigate. You must always contact them via their support email and live chat if they have one. You are probably not going to get much help from them but the least they can do is to delete your credit details so that you can enter them again. Also ask them to escalate the query to their technical department. Also ask them to wipe your checkout bucket clean and load it again with the product you are buying. 

If your card is still declined, then its about time to contact your merchant credit card processing company. The one you want to contact has to be provided on the checkout page by your merchant. Some of the most common credit card processing companies are Flagship Merchant Services, Merchant Warehouse, Chase Paymentech, Allied Wallet, Ignite Payments, PayPal, etc
Go to your merchants preferred credit card processing company website and head straight to their support page. You can read their FAQ page later. Look for their email & send them a quick email explaining your problem. Also start a live chat session if they have one and ask them to escalate your issue to their support page. 

You don't want to call any of these companies because you will end up losing lots of money. Calls might be redirected to call centers in India first and you will have a hard time trying to figure out the accent. 

If you have not yet exhausted your payment attempts for the day which is normally 5 times, use a different browser on the same computer to make the payment. 
If it is still declining, whip out your smartphone & try paying from two different browsers. 
If it is still declining, go to another computer on a different network like at your friends place and try paying from there. 

If none of these methods help you, the last resort will be to cancel your credit card and apply for a brand new one. 

If you have had problems with a merchant declining your credit card, use the comment section and share your experience. We might just learn a thing or two.