> For the complete documentation index, see [llms.txt](https://docs.tryterra.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tryterra.co/faq/help-topics/connecting/connection-errors-and-api-responses/generatewidgetsession-500-no-sources.md).

# Why does generateWidgetSession return a 500?

A `500` with an HTML error page from `generateWidgetSession` is typically caused by having **no data sources enabled** in the environment matching the dev-id you are using (testing and production are [separate environments](https://docs.tryterra.co/health-and-fitness-api/integration-setup/understanding-terra-environments)).

To fix it:

{% stepper %}
{% step %}
**Enable at least one source** in that environment, on the [data sources](https://docs.tryterra.co/health-and-fitness-api/integration-setup/setting-up-data-sources) page.
{% endstep %}

{% step %}
Verify your request headers exactly, since header name case-sensitivity can cause the same failure.
{% endstep %}
{% endstepper %}