Sharepoint 2013 online workflow trigger not firing on Create and Update

I have a customer having a SP2013 Online with a list that has had a workflow attached to a list that is set to Create/Update a record on another list. It has been working for quite a while flawlessly but now it is not firing.

I don't know how to access the ULS logs in SharePoint 2013 Online version. This is the first time I'm dealing with this. And I don't have access to Central Admin yet either. What possible steps can I take to dig deep and hopefully fix this problem?

Thanks for your help -Imran