Message Bus - How to communicate with other UE4 projects

I’m trying out the demo (total newbie in the game dev side) - downloaded it - the server side builds fine but the client side pops a message box “MessagingClient could not be compiled. Try rebuilding from source manually”. I’ve built the code in VS - and “appears” to build. When I try running the .exe manually I get a warnings about running with “COOKED” versus “UNCOOKED” version. I can reply with logs etc if needed. Thanks for any advice.
JackJ