No specific reasons are given for survey reversals by the research companies but this normally happens when your answers don't meet the required quality. Reasons for reversal include, but are not limited to:
• Failed quality control/test questions;
• Answering the survey too quick;
• Duplicate completed survey found (e.g. same IP or device);
• Information given not matching your demographics;
• Giving untruthful or contradicting answers;
• Not giving detailed answers where required;
• Giving nonsense/bogus answers;
• It's clear that random answers or straight-lining occurred on multi checkbox questions.
While doing a survey take your time to read and respond to each question truthfully with accurate information. You should read every question and respective answers carefully while making sure you understand them in order to provide quality answers.
Remember that giving poor quality answers will invalidate your surveys, even if you see the congratulations screen in the end. You may also lose access to further surveys if you receive too many reversals.