Presonus HP 60

Dear Cubasers,
I need some help with my Presonus HP 60. It works splendid. However, I can’t figure out how to get the individual mics routed to the different channels. For example. Mic 1 goes to track one in Cubase. VST Connection Inputs mono 1 connected to Presonus Firestudio Device Port Mic 1.
I want to use the External In facility of the HP 60 to give the singer more control of his volume so there is a cable between the Firestudio General Purpose Output 1 en the HP 60 External in 1. In Cubase the routing of track one is Mono Out 1, Presonus Firestudio Device port daw rt 1.
The HP 60 however doesn’t get this signal. Turning the Ext in knob doesn’t increase or decrease the volume.
How can I solve this problem?

Thank you, Leo