This issue is usually caused by an incorrect hostname or issues with network connectivity.

To resolve this issue, please follow these steps:

1. Double-check your Databricks host URL. Make sure it is spelled correctly and follows the proper format, such as `https://<region>.azuredatabricks.net`. Replace `<region>` with your Databricks workspace region.

2. Verify that you have a stable internet connection and that there are no firewalls or proxies blocking your access to the Databricks host URL.

3. Ensure that your access token is valid and has the necessary permissions to execute the notebook.