Some users may receive e-check instead of package activation confirmation to the e-mail.
Example of an e-check is below.
In this case you will see "BUY" button instead of "PLAY" in Launcher but your payment was successful.
If you haven't received an email with the key, please submit a request. You will receive a key from CS agent for further activation.
The key may be activated here - https://play.lifeisfeudal.com/redeem.
Below is an article with step-by-step instruction how to use the key that will be sent.