Using satellite 5.7 with rhsm

After upgrading satelliteserver from 5.4 to 5.7 I have some problems getting subscription-manager/RHN Classic/sertificates etc working correctly.
I have the server setup with rhsm and using a satellite-license, and have access to the correct repos.
But when I try to run satellite-sync I get:

]# satellite-sync -l --debug-level=4
16:58:50 Red Hat Satellite - live synchronization
16:58:50 url: https://satellite.rhn.redhat.com
16:58:50 debug/output level: 4
16:58:50 +++ Satellite synchronization tool checking in.
16:58:51
16:58:51
ERROR: there was a problem synchronizing the information.
Error message:
Error Message:
Service not enabled for system profile: "nk-rhel-vm-14.norkring.net"
Error Class Code: 31
Error Class Info:
This system does not have a valid entitlement for Red Hat Network.
Please visit https://rhn.redhat.com/rhn/systems/SystemEntitlements.do
or login at https://rhn.redhat.com, and from the "Your RHN" tab,
select "Subscription Management" to enable RHN service for this system.
Explanation:
An error has occurred while processing your request. If this problem
persists please enter a bug report at bugzilla.redhat.com.
If you choose to submit the bug report, please be sure to include
details of what you were trying to do when this error occurred and
details on how to reproduce this problem.

so satellite-sync is trying to use RHN Classic.

If I try to remove /etc/sysconfig/rhn/systemid, I get:

]# satellite-sync -l --debug-level=4
17:00:20 Red Hat Satellite - live synchronization
17:00:20 url: https://satellite.rhn.redhat.com
17:00:20 debug/output level: 4
17:00:20
17:00:20
ERROR: there was a problem synchronizing the information.
Error message: ERROR: this server must be registered with RHN.

How do I get satellite-sync to correctly use rhsm?

Any advice welcome!