Make sure you are connecting the Photogate (VPG-BTD) to the lab interface using a cable with a white connector (BTD) on the interface end and a black connector (RJ-11) on the photogate end.

We do have a different cable (designed for Motion Detectors) that has white connectors on both ends that can physically connect the photogate to the lab interface, but it will not work properly. If you use the wrong cable, the LED on the photogate will respond as normal when you block the photogate, but you will not get any data recorded.

Not compatible with photogates: Digital Sensor Cable (MDC-BTD)
Correct cable: BT Photogate Cable (PG-BTD)