Recently, I've had a spate of requests revolving around Windows 10, and Outlook attachments with Windows Apps. Photos, Edge, etc.
When a user tries to click on a web link, or open an attachment from Outlook when a Windows App is the default application, it throws the following error.
To resolve this, type UAC in Cortana and click on Change User Account Control Settings
Change this setting to something other than Never Notify
Change User Account Control: Allow UIAccess applications to prompt for elevation without using the secure desktop to Enabled