regarding the iotmms destination and nea-app.json, if you have "http" in the destionation then you don't need "entryPath": "/http" in your neo-app.json. Otherwise, if you have "entryPath": "/http" in neo-app.json then you don't need "http" in your iotmms destination.
And error code 401 means Unauthorized: Access is denied due to invalid credentials. Since you can get this error seems like your destination, neo-app.json and the GET url are all correct.
so I suspect there is something wrong with your OAuth token. Pls make sure you generated the token correctly, and also make sure your iot service is configured as well.
Pls refer to Configuring OAuth 2.0 for more details
I've the same issue using "postData". As I see in your screenshot, you have defined the "iotmms" destination with "BasicAuthentication" (and surely entered your HCP credentials here). I did the same and it did not work. The solution was to change this to "NoAuthentication". Otherwise the "Authorization" header with the device token you've created in your JS code is not passed to MMS but your HCP credentials.
It seems that some functions of the MMS need the device token as authentication (like "postData" and "getData") and some need the HCP credentials (like "pushData"), because if you open a new browser session and enter
https://iotmmsXXXXXXXtrial.hanatrial.ondemand.com/com.sap.iotservices.mms/v1/api/http/push/
in the browser address line, you get the authentication popup where you can enter your HCP username/password, but if you enter
https://iotmmsXXXXXXXtrial.hanatrial.ondemand.com/com.sap.iotservices.mms/v1/api/http/data
you directly get "Access to the requested resource is not authorized (HTTP 401)" because the Authorization header with the device token is missing.
Add comment