Does the number you want blocked appear in the Blocked tab of the app? If it does not you will need to go to the Call Log tab and select the number from the list or manually enter it into the text box at the top.
Please make sure that any security or task-killer apps you may have installed are set to exclude the Call Detector service. Examples of those types of apps are firewalls, task killer, anti-virus apps, and any app that is attempting to perform an action when calls come in.
Why is Call Detector not blocking text or SMS messages?
How do I block a number with Call Detector?
How do I unblock a number with Call Detector?
How do I know if I am blocking a number with Call Detector?
What if the number I want blocked isn't 10 digits in length?