Have you checked the S/PDIF input level on your audio interface, or possibly in your DAW?
Another thought would be for you to check which spdif output mode your KPA is set to. Mono, Stereo, GIT/Proc, ect.
Do you get normal analog volume?
Thanks, Dave, it is working as intented now. After a new start. Why, i dunno. Analog volume has always been like it should.