in my empire run there were several events and then the loyalist became the rebels. but in my loyalists run this not happened and i can´t reforme the goverment :(
rebell alliance dont have the pacific trait
try to reforme the goverment but

in my 2 playthroughs as loyalistsn i became rebel alliance, and was automaticly changed from pacifist to militarist. how it hapened i still don know saddly.

If the events aren't firing in game, you can use console commands. To start to form the Rebel Alliance you need to enter into the console "event swp_rebel.2".

This will give you the option to form the Alliance or maintain the status quo. If you choose to form, then 15 days later you will get the actual event that transforms the Loyalists into the Alliance, drops the Pacifist government ethic for Militarism, gives you a nice new flag, and new country colors.

Note that your Institutions will change, and you will lose a great deal of your envoys and as your institutions change to become more geared towards war instead of subtle influence gathering and diplomacy.