SharePoint designer 2010 workflow not starting when item is updated

enter image description hereI have written two SharePoint 2010 designer workflows both of which send emails to external users. The problem is both workflows are not getting started when I update the list item. One workflow is of simple one step which sends email. Also I have put logs there when workflow starts and ends, but no logs are added to Workflow History list. There is also one error coming when I publish the workflow “Errors were found when compiling the workflow. The workflow files were saved but cannot be run.”. This workflows are built for SharePoint online list. Any help would be appreciated.