When you click an InfoPath form from the workflows settings page in SharePoint Designer 2013, you receive the following message:
To open this file, you must first install Microsoft InfoPath 2013 on this computer.
Microsoft has a released a fix for this issue. You can download this fix from the following Microsoft websites:
For x64-based systems
For x86-based systems
Article ID: 2804405 - Last Review: Dec 29, 2016 - Revision: 1
Microsoft SharePoint Online