Ok so I tried on 2021.3.28f1 and SPUC 1.2.0 works all good no errors. Just make sure right after you import the package to run Generate in the Visual Scripting settings.
I did find out the problem. SPUC does not work well with Visual Scripting Plus which is a similar macropack. I had to uninstall both and install SPUC again. Problem now is that a lot of my game is broken as it cannot rebuild the connections and subgraphs.... what to do?
If you created any Backups you can restore from that. After reinstalling SPUC make sure you restart Unity before trying to opening any of the graphs, that usually reconnects all the nodes
