"To open this file, you must first install Microsoft InfoPath 2013 on this computer" message when you use SharePoint Designer to edit a SharePoint Online workflow
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:
Still need help? Go to Microsoft Community.