The ship was banned from operating in March after deficiencies in its registration and documentation came to light.
"But the vessel's registration in its declared flag state of Equatorial Guinea has now been verified," the authority writes.
The ship's captain was arrested in May on suspicion of using a forged document, after the ship was suspected of sailing under a false flag in Swedish territorial waters. The captain was later released and the investigation was closed.
The ship has previously been described as part of the Russian shadow fleet.