Hi Kristian,
The changes need to be applied to the servers. In the GUI there are two ways to apply changes made to service sets to hosts,
1) Edit a host and tick the 'Re-apply service sets' check-box, next to the 'Apply Changes' button.
2) Use bulk tools. The 'Refresh Hosts' tab will re-apply all service sets to all host showing in the main hosts table.
So, filter the hosts to refresh fewer hosts - complex regular expressions can be used.
After 1) and/or 2) have been done then the main 'Apply Changes' button needs to be pressed.
This is by design to stop unintended consequences when making a change to service sets.
HTH,
Mark.