I have a workflow associated with a content type. I try to kick it off from code from within the event receiver on the same content type, so when an item is updated, if there is a certain condition (status = ready for review) I start it.

//This line does find the workflow association

var assoc = properties.Web.ContentTypes["Experiment Document Set"].WorkflowAssociations.GetAssociationByName("Experiment Review Workflow", ultureInfo.CurrentUICulture);

//I had tried to use this line from something I found online, but it would return null

//var assoc = properties.Web.WorkflowAssociations.GetAssociationByName("Experiment Review Workflow", CultureInfo.CurrentUICulture);

var result = properties.Web.Site.WorkflowManager.StartWorkflow(properties.ListItem, assoc, string.Empty, SPWorkflowRunOptions.Synchronous);

//The line above gives me this error:

System.ArgumentException: Workflow failed to start because the workflow is associated with a content type that does not exist in a list. Before re-starting the workflow, the content type must be added to the list.

To check this, I was looking at the content type of the list item being updated and it is correct

properties.ListItem.ContentType.Name "Experiment Document Set"

So basically I have a workfow associated with the content type "Experiment Document Set". When I try to start a workflow from an event receiver in "Experiment Document Set", I get an error saying the content type "Experiment Document Set" does not exist in the list which doesn't make sense.