You might be using a default class other than TS. For example, your system might be running a window environment that uses the IA class by default. You can manually move all processes into the FSS scheduling class without changing the default scheduling class and rebooting.
Move the init process (pid 1) into the FSS scheduling class.
# priocntl -s -c FSS -i pid 1
Move all processes from their current scheduling classes into the FSS scheduling class.
# priocntl -s -c FSS -i all
All processes again run in the default scheduling class after reboot.