Trademark infringement is the owner's responsibility to discover. IP offices do not proactively investigate commercial infringement on the owner's behalf, though some will notify owners when an examiner identifies a confusingly similar new application.
It’s recommended that trademark owners perform regular searches of trademark registers, monitor online marketplaces and social media for unauthorized use of the brand, set up Google Alerts for the brand name, and use trademark monitoring services that automate some of this across multiple channels.
For Amazon sellers, Amazon Brand Registry provides dedicated tools to identify and report infringing listings. Customer reports are also a useful informal channel; loyal customers often notice copycat brands before the owner does.