getting error while sending dynamic notifications through custom activity in journey builder

I want to send dynamic notification through custom activity which I have created in journey builder. I am able to send only static notifications right now.

It is integrated with third party app through which the notifications will be send. I have integrated that using heroku and github. What changes should I make in config.json, activity.js and customActvity.js.

I have followed below site to create this custom activity and also the same github repository which is given there

https://www.vish-sfmc.com/post/new-changes-new-you

Below is the screenshot of error which I am getting after journey execution. Please tell me why I getting this error, if I need to do changes in node js or in marketing cloud.

https://stackoverflow.com/questions/67429068/getting-error-while-sending-dynamic-notifications-through-custom-activity-in-jou May 07, 2021 at 12:34PM