Runscript() not working after upgrading from 7.9 to 8

As per the above. I have a series of expression tags that run shared scripts to return values. These worked fine before the upgrade to 8, but won’t work at all. I even created a new expression tag and script using this example from the help, and again can’t get it to work:

https://docs.inductiveautomation.com/display/DOC80/runScript

I’m sure it’s something obvious, but at the moment i’m stuck!