Like its two predecessors (launched on Aug. 25 and Sept. 1, 1962), this Soviet Venus probe never left parking orbit around Earth.
The Blok L upper stage designed to send the spacecraft toward Venus fired for only 0.8 seconds before shutting down due to unstable attitude. Later investigation indicated that the upper stage had been put into a tumble due to the violent shutdown (and destruction) of the third stage (Blok I) between T+530.95 and T+531.03 seconds.
The tumble mixed air bubbles within the propellant tanks preventing a clean firing of the engine. Unlike its predecessors, this probe was designed for a Venus flyby rather than atmospheric entry and impact.
The payload reentered two days after launch.
Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.