I have a couple of sites deployed on in the sharepoint online cloud.  Some of the sites I am able to select the 2013 workflows, but on others I am not able to.  I have checked all of the site setting and they are identical for those that have the 2013 workflows enabled and those that don't.  Is there a setting that I am missing?  All the online help I can find is devoted to on prem solutions.

Would you contact Office 365 support, I would make a ticket for them to see what's going on. All sites created in O365 now should support 2013 workflows.

Hi cthomas,

As my understanding, the SharePoint 2013 workflow platform is missing in SharePoint 2013 Designer with Office 365. Is it right?

In SharePoint 2013 On-premise, we need to configure Workflow Manager to enable SharePoint 2013 workflow platform. In Office 365 SharePoint Online, per my knowledge, Workflow Manager service is controlled by Microsoft. So, for this issue, I suggest you create a new thread on Office 365 forum. The reason why we recommend posting appropriately is you will get the most qualified pool of respondents, and other partners who read the forums regularly can either share their knowledge or learn from your interaction with us. Thank you for your understanding.

Office 365 forum:

https://community.office365.com/en-us/f/

In addittion, there are some similar posts, check if they are useful for you:

http://www.t-collaboration.com/Blog/Post/4/Office-365-%E2%80%93-SPO-SharePoint-Online-%E2%80%93-Platform-Type---%E2%80%98SharePoint-2013-workflow%E2%80%99-option-missing-from-SharePoint-Designer-2013

https://community.office365.com/en-us/f/172/t/190810?pi239031356=2

Thanks,

Wendy