All you can do is give all the buyers a full refund and allow them to keep the items. Let amazon know exactly how you remedied the situation. Let them know you will exercise due diligence before listing any future items.
Your problem is you do not know for first hand fact that those items are not fake. Typically stuff purchased from a liquidator is fake, amazon has seized it and just sold it to a liquidator and you just bought it, rinse and repeat.
If it is just “At Risk” of deactivation and not asking for a Plan of Action, then delete any listings subject to complaints or any similar listings and wait for the defects to disappear from your metrics after 180 days.
To avoid Amazon account deactivation due to a low health score and IP complaints without invoices, submit a thorough appeal, contact brand owners for cooperation, remove infringing listings, enhance customer service, and monitor your account regularly.
each situation can be unique, and the outcome depends on various factors, including the cooperation of the brand owner. Amazon’s appeal process can take time, so be patient and persistent in your efforts to resolve the issue and improve your account health.