@TomBrick Can you use the latest ODBC driver. Below is the link to download it.

https://www.databricks.com/spark/odbc-drivers-download

Also, can you add the parameters below in the simba.sparkodbc.ini file? This will give you more information about the issue. Please check the driver connection logs after reproducing the issue. 

AllowDetailedSSLErrorMessages=1

I see below in the logs which could be due to a variety of issues.

DriverOAuthSupport::OAuthConnection::ReadTokenRefreshSqlState: Connection error SQLState is defaulting to SQLSTATE_CONN_FAILURE (08006)

For further troubleshooting, you may log a support case with us.