Yes, I'm using a webwallet and vendor processor called coinpayments.net.
So the site that I made a purchase from uses this webwallet/processor and when you finalize your purchase, you're automatically directed to coinpayment's site to make the payment. It's what the site I'm purchasing uses so there's no other choice. But during checkout there is no option to add a transaction fee which means that my payment isn't going to go through. When I look at the transaction it says 2 confirms needed but I'm not going to get those confirms without a transaction fee, right? That's why it failed last time.
When I look at this seller's score (which coinpayments allows sellers) it's like 99% with thousands of purchases which means I'm doing something wrong because others have obviously made successful purchases from them.
Also, I've used coinpayments for other purchases with no problem.
Simple. Your webwallet doesn't allow you to set custom TX fees. Create a new Electrum wallet, generate and keep your seed and send all your coins from your webwallet to the address in your Electrum wallet. Electrum lets you set fees to whatsoever they want you to pay in order to get your transaction confirmed at their end and complete your purchase.