I'm testing this currently, so what I'm going to say below is suspect. I'll try to come back and confirm once enough time has passed to be sure the problem is fixed. I'm posting this now in case I forget to come back to this post. =)
The Utility - JSON object's Business Object Properties (the information stage on the Initialise page) > Code Options tab > External References previously had this as an external reference:
Newtonsoft.Json.dll
I've changed it to this to see if it's as simple as BP not being able to find the dll:
C:\Program Files\Blue Prism Limited\Blue Prism Automate\Newtonsoft.Json.dll
Dave Morris, 3Ci at Southern Company