Raspberry PI GPS Module - problems using active antenna

I recently purchased 4x Raspberry PI GPS Modules, and are experiencing problems when using these with external active antennas. During testing the GPS signal quality does not change or improve with the external antenna connected. The ADDET pin is also always low, indicating that the L80-39 module has detected the external antenna, even when the antenna is disconnected. Any ideas what the problem might be?

I have tested using this antenna: https://no.farnell.com/siretta/alpha4a-5m-smam-s-s-26/antenna-adhesive-sma-5m/dp/2666799?ICID=I-HP-STM7REC-RP-2