The issue is that the Integration service user is unable to create the workflow log file
There could be multiple reasons for the same.
1. Not enough disk space.
2. Permissions issue.
3. Illegal path.
Please check the above.
When I say permissions issue, I am referring to the user who has started the Informatica services.
You can change the workflow log file directory in the Workflow properties and set it to some path where the user has aqequate perrmissions.