Hello @KiwiTech
Thank you for your response and persistence troubleshooting this device.
Since the MST30C2HHPD appears to be functional with the HP Probook 455 Gen 9, it appears there may be an unforeseen incompatibility issue with the HP Probook 650 Gen 8. It may be worth looking into an alternative docking station such as our DK30C2DPEP. The primary difference is the the DK30C2DPEP utilizes DisplayLink technology to output displays.
Furthermore, the TB3DK2DHV is a ThunderBolt 3 dock and requires the host to be equipped with a ThunderBolt 3 port. Sadly, the HP Probook 455 Gen 9 and the HP Probook 650 G8 are only USB-C capable. I would recommend taking a look here which highlights the difference between USB-C & ThunderBolt 3.
Please let us know if there is anything else we can assist you with!
Atha T