Which of the following is NOT a reason for clubs to receive sanctions?

The correct answer is the failure to register players. This action typically does not lead to sanctions because registration can often be rectified within a particular timeframe, and many leagues or governing bodies have procedures in place to address administrative oversights. It is not seen as a violation of conduct like other options listed.

On the other hand, violating agent regulations, employing underage players, and paying salaries late are serious infractions in the world of sports. Violating agent regulations undermines the integrity of the agent and player relationship and can lead to penalties for both players and clubs. Employing underage players raises significant ethical and legal implications, as it can lead to exploitation and diminish the fair play principles that sports organizations uphold. Paying salaries late violates the contractual obligations between clubs and players, which can result in sanctions to protect players' rights and ensure proper governance in football.