I don’t see any mouseover listener in the notebook you shared. Have you shared the latest version?
I did notice another bug in your code: in the spawn function you are appending a text element to node after joining, which means you’re adding text elements to nodes that already have them. I expect you only mean to add the text element to the new node, which would need to be part of the enter clause of the join.
Edit: I also realized you’re adding text elements to circle elements, so those text elements will be ignored. You’ll need to change node to be G elements, and then add both circle and text elements to that group element.