With separate scs instances the scs instance does not get registered in the sld by default (in all versions)
Sapstartsrv will register the details for the scs instance (and any other instances that it knows about) if an slddest.cfg file exists in the instance GLOBAL directory.
You can create this file as sidadm by running this command from the GLOBAL dir
sldreg -configure slddest.cfg â€“usekeyfile
sapstartsrv will only do this on a HARD restart, which means you have to shut the system down and restart sapstartsrv (not just do a startsap; stopsap)
Without this step you canâ€™t do a managed system config in solman (properly) as the system will fail the pre requisites check.