Run the Editor Tool as an Administrator to ensure it has permission to apply the key to the game directory.
FIFA Editor Tool asking for an Encryption Key : r/FifaCareers
For FIFA 23, a verified encryption key is essential for users of editor tools. This key is typically provided by the developers of the editor tool or is extracted from the game itself by enthusiasts. The verified key ensures that the edits made to the game are compatible and can be properly decrypted by the game, preventing potential errors or crashes.
It is common for antivirus software to flag modding tools as potential threats. Many modders suggest adding the tool to your antivirus "exceptions" list or temporarily disabling protection during the initial setup. Anti-Cheat Awareness: FIFA 23 uses EA Anti-Cheat (EAAC)