It didn't throw any specific message, it just said Error with credit card in red and then refreshed the page automatically...
I sent couple of emails to support@itch.io but no response
Viewing post in Issues with my order
Usually, a single mail to the support team should suffice.* From what I can tell there are currently a lot of support requests - so the team would need a few days until they can even read your mail, then contact the admin (if the transaction really went through, then this behavior is some kind of bug) who in turn has to take some time to figure out what happened. And then they can respond.
.* Giving the other party some time to check the situation before sending a second request for support about the very same topic is not only a good idea but common courtesy.