You have configured SharePoint 2013 and Workflow Manager. You have created a new Site Collection. You’re unable to create SharePoint 2013 workflows (but SharePoint 2010 workflows works).
Problem: The site collection was created using the blank template, which doesn’t include all necessary dependency features for creating workflows.
Fix: You need to enable the hidden feature WorkflowServiceStore using PowerShell.
Enable-SPFeature -Identity WorkflowServiceStore –Url $yourUrl
Credit goes to Anuja Bhojani (blog) for finding this nugget.