If you sent your friend a referral link but it didn't work, they can still enter the code manually! They can enter this code here: Home > Friends > Enter Referral Code. This should link your accounts and you'll get the boost! Please note that this option is available for the 5 days after your account creation.
If this still doesn't work, then here are some common reasons:
Your friend has had an Ember account in the past
Your friend's Ember account is older than 5 days
Your friend has already been referred by a different user
Your or your friend's device has multiple accounts linked to it
If you successfully added a referral code, but your friend is still missing on your end (or vice versa) then it's likely that one of your devices has multiple accounts tied to it. In this case, please send the email addresses tied to both your and your friend's Ember account to our Support team.