I'm trying activate Nintex Workflows on a SharePoint 2013 (on-prem) site and keep receiving the error message below when trying to create a new workflow.  Specifically, I get this error message when trying to save the new workflow before publishing it.  

We've had workflows installed on a number of other SharePoint sites for years, but for some reason keep getting this error on a new site we've enabled workflows on.  I searched the Nintex Community and found a similar post, but it was related to someone just installing Nintex for the first time.  I wouldn't expect to see this error in our overall SharePoint environment which has been utilizing workflows for a long time.

Any help or guidance you could provide would be greatly appreciated!  Thanks!