It all depends on what's going on in general, in the past year I have had response times from the next day (the best you will likely see most of the time) to 7 days (about the outside unless there is some major incident clogging up the petition system like a server merge that borked hundreds of player's inventories).
Did you answer the auto generated email? Usually they send one out and it lists possible fixes and you need to answer that none of them worked and its still an issue so it stays open. Did you check the status of your ticket? If its a first time purchase of krono it could take a few days. If they have to go into your account and verify if you really had something then it can take longer.
