Entries could be marked invalid for a number of reasons. Our fraud protection mechanism automatically invalidates entries performed by an admin, or if a contestant provided a bounced email address.

Some times, entries may be invalidated even if no fraud was involved. For example: Multiple people from the same household tries to enter a contest from the same IP address. In this case, only the first person will gain valid entries, but the campaign host can still manually validate the subsequent entries if it's not against their campaign terms.