Hi, @sns ,
For event log of a workflow, you will need to check the workflow history list. You can access it via browser or export it with a PowerShell script.
The URL is like this : http://[servername]/[sitename]/lists/Workflow%20History
Or open the site using SharePoint designer and then go to All Files from the Site Objects tab from the left side, you will able to see the list.
And for the issue with the workflow. Not much I can say without checking the actual setup of the workflow. It will be better to provide more information about the workflow.
As it works when you start it manually, it shall be fine on the actions sending email. The issue shall more be related to triggers you use. Or the if condition which control whether the Email shall be sent, if there is one. So please provide the actual structure of the workflow and more detailed information about the failed trials of the workflow and succeed ones.
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