Please follow the following step to install Thunderbolt adapter on HP Z820.

1. Ensure PCA jumpers are set as: Force FP-> left 2 pins, SLP S5-> left 2 pins and SLP S3-> left 2 pins

2. Connect (1)-Wire Cable w/2 loopbacks to PCA connector P24 and Connect (3)-Wire Cable to PCA connector P26

3. Connect Required GPIO Cable header to Thunderbolt card connector

4. Install Thunderbolt card in the correct slot 5