@QianL Sample mining should work in your sub-production environment and allow you to mine up to 3600 records per project.  (Note Process Mining is not available for Personal Developer Instances (PDI)).   You also should validate that audit log data is available in the instance you are attempting to run Process Mining on.   The other potential cause for the message you are seeing is your id may not have access to the records you are trying to mine.  

 

This Process Mining Academy session may have with the project creation instructions.  https://www.servicenow.com/community/process-mining-article/process-optimization-academy-7-15-22-how...