This is the primary and recommended method for most users. The Creative Cloud desktop app acts as the central hub for installing, updating, and launching all your Adobe applications.
While most users will always be connected to the internet, Adobe does provide a more complex, manual activation method for "air-gapped" or highly secure computers that cannot be connected to the internet. This is not for general consumers and is typically used by large organizations with enterprise licenses. how to activate adobe photoshop
This error occurs when Photoshop is active on too many devices. This is the primary and recommended method for most users