Ai perception stopped working after save/quit and restart the project

So I set up a perception and stimuli system that was working perfectly well yesterday.

I could even debug it propperly and would get all the info I needed.

Quite happy with myself (I am a beginner) I saved, quit and went to bed.

This morning however, my AI is not seeing my character anymore.

So this used to register a stimuli and a little green sphere would appear (not anymore)

Here is my AI controller with perception:

And here is my character with stimuli :

Thanks in advance for any help.
I am looking forward to feeling stupid (hoping some silly thing I forgot to do or save)

Found the problem : it came from Project Settings > AI settings > AI perception class was set to “None” for some reason.

And yes I feel silly.