Can someone please explain to me how influence conversion works? It is driving me nuts.

I have a system that is completely inside my enemy's influence bubble but it is not in the process of being converted as far as I can tell. Looking at their planets they are producing a combined total of 35.5 influence my system is producing around 90, and is buffed by a hero, and is buffed by a few influence producing buildings and all planetary specializations are for influence and yet I can't push the enemy's bubble back it's just stuck there. And it is really stressing me out because it's only a matter of time before the AI decides to start the conversion and it is a very important system being a important citadel system and all.

Do multiple systems combine their influence if their bubbles merge? Where in the game do I go to get more detailed info regarding this. I need to see why I am not pushing their bubble back.