I can access the Data API for my app just fine while in development mode (i.e. when including “/version-test” in my URL) but when I try accessing it in live mode (i.e. when not including “/version-test” in my URL) it fails with a message:
{"statusCode":404,"body":{"status":"NOT_FOUND","message":"This application does not expose a Data API"},"args":{"bubble_code":"1556751416663x279200421685240830"}}
Make sure you have done a deployment to Live in order for the Data API setting to be activated. You can double check this by seeing if the Live version of Settings shows an activated Data API.