The link you added was too short. The link to the course is this one. So there you get the error in module 5.
You likely missed a step in setting the values of the activity ‘Call Rest’ in microflow REST_GetProducts (but I do see which). So run by the exercises one more time to see if you missed a step (but you probably already did that).
2 To make it easier to see your variables that you feed to the ‘Call Rest’ activity, in your microflow, first add ‘Create variable’ and use those variables in the call ‘Call Rest’
Looks like you have not applied the security properly.
If there are any more unclarities, I hope you know that you can download the working model in the next chapter.
So you can cross check what did you miss.