Hi,
there are some great tutorials how to interact from your Mendix app with Mindsphere (InsightsHub)
https://academy.mendix.com/link/paths/80/Build-a-MindSphere-app-with-Mendix
and
https://academy.mendix.com/link/paths/93/Build-a-MindSphere-App---Continued
Which API do you use?
https://documentation.mindsphere.io/MindSphere/apis/iot-iottimeseries/api-iottimeseries-api.html
HTTP 415 means that the server does not understand your meda type.
Have you specified a “Content-Type” header? it should be “application/json”
How do you build the body? I suggest to use an export mapping to create the JSON object.
I’ve done this by calling /api/iottimeseries/v3/timeseries/<AssetID>/<AspectType> with Content-Type application/json. My data is created in JSON using an export mapping, which includes the timestamp and fields for the aspect