There are a number of reasons why your transaction might have failed.
1. Your eth address is not whitelisted
2. The gas price you used isn't high enough.
The gas price you used isn't high enough
If your transaction failed, then you should see an out of gas notice if you check your transaction hash on etherscan.
Transactions on the ethereum network require a gas price and a gas limit. If the gas price is too low then the transaction is not attractive to the miners of ethereum transactions, and your transaction will be ignored and eventually dismissed. Think of the gas price as giving a bribe to the bouncer of a club. If you give a lot, you'll be processed quickly, but if you give too little, you will be ignored and have to queue like everyone else.
If your gas limit is too low, then the miners of ethereum transactions will try process your transaction, but the amount you are willing to pay them to complete the transaction is too low for the amount of work they need to do. This is commonly referred to as being out of gas, and can occur on any transaction. This is like paying someone for a job, but they look at the payment and refuse it. If it's too low, then none of the miners will take on the job of processing the transaction.
The solution is to increase the gas limit. Check the instructions for your wallet provider. For MEW, you can increase the gas limit by:
1: Fili in the ETH amount to send.
2: Fill in the address to send the ETH.
3: Click the Data & Gas Limit button.
4: Enter 200,000 for Gas Limit (MEW normally calculates the correct gas limit for transactions, but this might fail if you, or your wallet provider, have set a gas limit. Normally, as gas limit of at least 90,000 will work If this limit doesn't work, try increase the price a little more).
5: Send Transaction.