According to the encyclopedia: 

Influence and Diplomacy

Soft power is a great way of justifying invasions: once another Empire’s Territory is in your Sphere of Influence a Grievance against them will be generated which you can use to Demand it from them! Territories in your Sphere will also affect the War Support your opponent has if a War ends up being declared.

Territories that are part of your Empire’s Sphere of Influence do not confer direct economic advantages, but you’ll need to add them to your Sphere first before more distant Territories can be affected. In addition, adding an Independent People to your Sphere of Influence will passively improve your relations with them each turn.

There are a grievance called "oppressing my people" which you are supposed to get when a territory that belong to another player is under your sphere of influence, however I have not been able to get this one at all, even though I have many territories under my sphere of influence that belong to other players. According to the encyclopedia it should be just enough to have the territory under your sphere of influence, but that do not seems enough. Like there seems to be some other requirement.

Similar for religion, if another player have territories under your state religion and they do not have your state religion, you get a similar "oppressing the faithful", this one I have gotten alot, however yet again there is a player who I don't get this grievance against.

Here is my sphere of influence, as can be seen have many of green territories under my sphere of influence.

Here is religion, I have atleast one green territory under my state religion and they don't have it as their state religion

Here is the diplomacy screen, as can be seen I do not have any grievance against green.

Any ideas why I don't get grievances against the green player?

Save file if someone want to take a closer look at what is going on Frence.ctr

Maybe they chose the irreligion civic

I think I know how it work, once you pick a civic, they (who are in your sphere of influence) will get an event forcing them to pick the civic or if they don't you get "oppressed my people" against all their territories in your sphere of influence.

I would still say I'm unsure about the exact rules for when you get oppressing my people, if anyone know what exactly cause it to trigger I would be interesting to hear it.

Here is some more testing:

• Removing the imperalism civic make the "oppressed my people" grievance tick down the next turn with all players.
• Keeping the imperialism civic make  the "oppressed my people" grievance stay at 10 turn with all players.
• I declared war on one player and lost a battle to see if they had anti imperalist civic, but they did not.

Did someone figure out what are the exact rules of getting opressing my people grievance? 

It might have to do with the Mono/Muticulturalism civic that the other empire has.

I'm the user who posted this and I still don't know the rules for oppressing my people.

Waterloo wrote:

It's interesting if it's tied with some civic choice, but the game keeps it secret from you. 

Maybe the developers can tell us the rules?

Yes, The-Cat-o-Nine-Tales especially likely to look after it, and tells us, often answers such questions here.

Apologies for necroing an old thread. I'm not sure if that is preferred to opening a new issue. I'm experiencing this same thing. I've had another empire's territory in my sphere of influence for many turns and haven't gotten any grievances. I started out the game interested in using soft power, but keep getting pushed to just invade someone because the soft power appears to be broken.