Sometimes you might think you completed the survey while the survey screened you out. See, Why do I get screened out of a survey?
After you complete a survey, you usually see a text informing you of the successful completion before getting redirected to Prime Opinion.
If you completed a survey but did not get redirected back to Prime Opinion to receive your Points, please take a screenshot of the confirmation page and contact our Support Team so that we can look into this for you.