I'm having the same issue on a SharePoint 2010. The workflow isn't started by a system account or pro grammatically. It is setup to start upon creation by a regular user. The items sits for days unnoticed, and the workflow never starts on its own. I've even setup a secondary workflow to start after 5 minutes just in case the first one didn't start. If SharePoint has decided that it doesn't want to start a workflow on an item, it just doesn't start any of the workflows on that item..
I've also changed the workflow timer to be 1 min instead of 5 minutes, but that doesn't help as I understand that this will only assist to make the workflows with State machines run faster..
check your SP logs for "Workflow Infrastructure" errors around the time you created the item. Hopefully there is something there that could suggest why SP isn't starting the workflow.
I have the same issue for Nintex O365 workflow everything was going smooth and nice tell yesterday
the all process suddeny stopped from running automatically based on condition the process usally start automaticully for modify or created today user reported that his process wont start
any clearificationfor sharepoint online Office 365
Any news on this? Same thing happened, the workflows started automatically and they suddenly don't. We haven't changed anything.
They start automatically when adding a document in the library manually, but not when we add it from another source.