Update: I have used actor display names and a string key instead of the object key, but the string key is also not being set. I can see the blackboard whilst the game is running, and whilst the vector key in the blackboard is working, the string key is not, despite me being able to print the same string to the screen immediately before setting the blackboard value:
The blackboard is set up correctly, and the behaviour tree is using the correct blackboard:
If I’'m not missing something, I guess there is an issue with the blackboard system.