When creating a flutter project,
Make sure: applicationid for android conforms to: https://developer.android.com/studio/build/application-id

Make sure: bundleid for ios conforms to:
https://developer.apple.com/library/archive/documentation/FileManagement/Conceptual/understanding_utis/understand_utis_conc/understand_utis_conc.html
(Not only the name,but also the organization, as it's a check for whole bundleid.)