Hi @le_ba_nam
Before starting the datafeed, the code will try to open the job. The error message from the job open step should contain more useful information. To narrow down troubleshooting, please try to just open/close the job; rather than start the datafeed as well.
Where there any Kibana UI toast error messages when you tried to start/open the job?
Is the job state set to FAILED in the job list? If so, please try to force close it and open it again.
Are there any error messages in the Job Messages tab?
Do you have access to the elasticsearch logs? and if you do, are there any error messages which explain why the job entered a failed state.
To help with any further troubleshooting, please let us know what version of elasticsearch you are using.
Regards
Sophie