If you downloaded and installed Zombie Moon from a player's referral link, a referral code is automatically applied and referral bonuses and connectivity are applied right away.
(Finding your referral link: Look at the referrals tab for your link, click the email icon and you will have it contained within.)
Zombie Moon is streamlined for one-click play start with a minimum set of data requests. We do not prompt players to enter someone else's referral code after they have started play - it is determined before play begins using the link and process described above.
A referral code is used to indicate another player who let you discover the game and to thank them for introducing you to a game you would otherwise not have found they earn bonuses as you level up.
We have found that players were sometimes misreporting the code after joining to try to give those bonuses to players they like but who did not earn them.
Something like, "Hey, can I credit someone for joining here and give them a free bonus? I like you guys and don't want you to miss out so I'll say that one of you referred me." Good intention but not accurately reporting and not fair to the others.
Our guard against someone making a mistake while simultaneously protecting against multiaccounts and/or misuse as noted above and to help offset and guard against the costs we incur for spurious manual changes is to offer to update the referring code manually for a player if they:
1. open a ticket with the player name and code in question
2. request a referral code adjustment within 14 days of starting play
3. make a purchase within 30 days of play
The last condition is probably the most important for weeding out multiaccounts aimed at rigging player levelups and is critical to avoid the emerging problem of "trivial ticket abuse" which would otherwise exhaust our ability to offer support.