I am trying to build a Custom activity for journey builder. I was using the great tutorial by Markus Slabina Salesforce Marketing Cloud - Service Cloud Custom Split Activity as a start. The activity is hosted in Heroku as advised. The activity loads ok into journey builder, but when I try to activate I get the error "A custom activity or entry source failed validation. Check to ensure that the activity or entry source publishes to a valid endpoint."

When I check the logs in Heroku, I see "JsonWebTokenError: jwt malformed"

I can write the body to the console ok, and I have set the secret up just as the tutorial said.

Has anyone else seen this problem and can anyone point me to the up to date procedure for creating keys / salt within marketing cloud and where to use them within the Custom Activity? I believe the salesforce instructions and the tutorial instructions are out of date and this may be my problem.

Any help is greatly appreciated.


  • Have you tried decoding the JWT token to see what is wrong with it? jwt.io
    – BrBarr
    Nov 13, 2019 at 21:56
  • Thanks for the comment. I cant see where in the code the app is receiving the jwt from Marketing cloud so I can write it out? or do you mean when the app is sending the jwt? Sorry for the stupid questions
    – DavidB
    Nov 14, 2019 at 6:50

1 Answer 1


Ok, so as it turns out if you make changes to the config.json you MUST create a new journey to reload the configuration, you cant just test in the same journey. If you dont and make changes to any other code the changes are reflected in the journey when you activate and test. But changes to the config.json require that you create a new journey and re-validate. Hope this helps

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