Workflows are NOT executing anymore. Which module is the root cause for this problem?
If this is for ACC(V6/V7) , just check if workflow process(wfserver@ instancename) is running or not .
You can see that from motioning tab of home page
You can also go through below link to troubleshoot common issues related to workflows
Workflows not starting in a campaign: Technical workflows
Campaign workflows stuck in "Start as soon as possible" status