If you are experiencing loss of caller ID with your call blocker connected on your telephone line and have tried the Parallel Set up without success, this is most likely down to intermittent caller ID caused by a faulty/poor quality ADSL/DSL broadband filters. First suggestion is to disconnect everything from your line, all equipment (modem/router, fax machines, printers, stand alone answering machines, Caller ID boxes, alarm systems) and remove all filters from all wall jacks in the property.
Then connect just the Call Blocker from the main telephone wall jack in series to a single telephone. Then please connect each filter and device, one at a time, checking the line after each one is connected to help you identify which filter or device is causing the interference on the line. If needed replace the filter if necessary with a top quality ADSL/DSL filter such as NETGEAR, BELKIN, D-LINK or ADSL NATION XF1e branded filters. This problem can also be down to having too many devices attached to your line as the Call Blocker takes its power directly from the telephone line itself.
If you have any further questions, please feel free to contact our technical support team.