Mendix Call POST Request Results in 500 Internal Server Error

Hello i wan't to create an Mendix Microflow which executes a post request to an external REST endpoint. I have tested this endpoint with Postman and Advanced Rest API tools and get the no errors back. Within Mendix i created a Microflow with an Call Rest Activity(see pictures below).When i run the application it returns an error "An error occurred, please contact your system administrator." To debug this error i created a trace on the Rest Call in logging window. When i look at the consume Rest API logging i receive the following error:   Please can you help me to solve this error?                      
1 answers

There is nothing in your template. You should either place {1} in there or just put the expression in the template. Looks a bit strange though as it now looks like a constant value. See also the documentation here: point 6.4.