Below are some reasons that may cause your call blocker to block calls:

1) Make sure Feature # 6 is turned OFF (refer to section 6.0 in the manual).  This feature can cause random numbers to be blocked.  Please refer to this article to learn more.

2) Avoid having numbers with less than 5 digits in the BLACKLIST.  Please review your BLACKLIST (press the BLACKLIST button and then the scroll buttons) to make sure there are no numbers with less than 5 digits.

3) If you are blocking area codes, please make sure that the numbers being blocked are not within the area codes that are being blocked.

4) If none of the above works, you may have a corrupted BLACKLIST.  If so, please remove all the blocked numbers in the BLACKLIST.  
If none of the above works, please contact us.