Ok so basically. “Get Player Character” / “Get Player Controller” is a quite bad idea if you work in multiplayer. You probably saw the integer input. If you work with multiplayer you have multiple player characters / player controllers so you need that number.
They only work for single player games as magical “Get this” node.
You somehow need to get the reference from your player to the AI. Personally I would do that by using the Game Mode.
Game Mode has an event “Event Post Login” which will provide you a “Player Controller” reference.
If you spawn in your AI via the game mode instead of placing it in the level you also have a guaranteed OOP legit reference to them.
And from then on you can for every Post Login which gets to play the player controller reference and feed it to your AI.
Cheers