Command & Conquer 4: Tiberian Twilight was designed with a "persistent online" requirement, meaning that even for single-player campaigns, the game officially requires a constant internet connection to save progress and access unlocked units.
Playing offline is famously difficult because the game was designed with a mandatory "always-online" DRM system. Even for single-player campaigns, all progression is stored on EA's servers. Command & Conquer 4: Tiberian Twilight was designed