Run SQL statement failed in Machine Learning

Summary

When running a SQL statement in Machine Learning, I got an error said "Invalid life cycle state. Check the status of the Universal Connection Pool"

Content

Hello, 

I am preparing a Machine Learning Notebook example for my customer. But I got an error when running a SQL statement, as the attached image. The SQL statement could be executed successfully by the ML user via Sqlplus. How to resolve this issue? 

Thanks, 

Hua