Need support: Studio Sends & direct monitoring problems

What am i doing wrong:
Configure a microphone input (SSL Alpha channel on spdif coax L)
create an audiotrack and check the input arrives correctly (enable the orange monitoring button)
create a 2nd audiotrack with the instrumental version of the track
use studio sends to send both to “Studio 1”
map studio 1 to headphones 1 in MR hardware setup

now the problem:
the instrument track arrives in headphones 1 and i can see the meter in studio1 move and control the volume with the “studio send slider” on the audio track
However with “direct monitoring” enabled the singer can not hear himself on the studio headphones, his signal does also not appear in the studio 1 meters, unless i dissable “direct monitoring”
so we can either track with direct monitoring ENABLED, but no recording signal arriving in studio1
or DISSABLE direct monitoring, which sends the singers vocal through, but introduces latency.

What am i doing wrong here?

This now works, was a specific with my SSL alpha channel, connected via spdif to the MR