- Check the database URL in `environment variables <../installation.html#envvar-DATABASE_URL>`__ if the following error is displayed in **gunicorn** logs:
- Check the path in `environment variables <../installation.html#envvar-UPLOAD_FOLDER>`__. ``UPLOAD_FOLDER`` must be set with an absolute path.
`Failed to upload or download files`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- Check ``client_max_body_size`` in **nginx** config. Increase the value to handle larger files (see **nginx**`documentation <https://nginx.org/en/docs/http/ngx_http_core_module.html#client_max_body_size>`_).
- Increase **gunicorn**`timeout <https://docs.gunicorn.org/en/stable/settings.html#timeout>`__ value if the following error is displayed in gunicorn log: ``[CRITICAL] WORKER TIMEOUT``.