I think the best strategy to take when a Validation or Verification report have failed to achieve the expected results is to think about the Requirements you need for your design, because common problems in the verification “story” come from poor requirements.
Also, Plan It Before You Do It, always plan right before starting verification process, because testing is often very expensive, time consuming, and subjective. Use testing where it makes sense to do so. So, Know the requirements & Plan it the best strategy to use.