Pokémon GO Error 12 can occur due to various reasons such as disabled location permissions, weak GPS signals, or outdated game systems. To fix this error, users can use tools like iMyFone AnyTo, which supports both iOS and Android platforms and offers various modes for players to choose their destination or simulate movement. Resolving Error 12 involves specific steps based on the device's operating system, such as checking location services for iPhone users or allowing precise location for Pokémon GO for Android users.