There is an issue introduced in Now app version 10.0.0 to 10.0.3 where opening an attachment shows an error on the Browser shows "Your file was not found".
1. Log onto instance from Now app from version 10.0.0 to 10.0.3.
2. Go to Home and use the search for KB article which contains an attachment
3. Open the attachment
Expected Result: Attachment opens for viewing in the browser
Actual Result: Browser shows "Your file was not found"
This is fixed in version 10.0.4. Please update your app to the latest version have this issue resolved.