Glad to hear that the enemy AI can detect the player character now.
As for the AI not turning on at all after migration, changing the Game Instance Class in your Project Settings to BP_GameInstance should fix part of the issue. However, this toolkit is meant to be used as a base framework to build on top of instead of being added to a project like an asset pack. The project uses custom collision channels (you can see under Project Settings >> Engine >> Collision) and Unreal cannot copy those settings during the migration process. Since the AI relies on these custom channels to detect stimuli, they won’t be able to detect the player character. So I’d suggest porting over external assets to the toolkit.
You should be able to get the proximity detection working by making the following change in the StimulusGenerator component of your player character:
This will ensure that the player will be perceived as a stimulus source by the AI’s close-range motion sensing.