Hi @psmtvdw
you cannot use a JSONata expression as the key passed to the flowContext function.
You would have to get the full object from context and then use a JSONata expression to pull out the piece you want:
$flowContext('Products').Products[ProductID=$$.topic].ProductName
This assumes the product ID you want to lookup is in msg.topic and that it is a number type - not a String. JSONata is strict about types.
For future reference, please read this post about sharing code/flows in the forum: How to share code or flow json
