Setting the clock manually on your device can cause multiple issues with different apps. If you're seeing an error where no videos load while also getting the error message "Fail to load video. Please try again later", you might have set your time manually before and this could be causing issues with the Viki app.
Here's how to do it:
1. Go to Settings > General Management
2. Go to Date & Time
3. Select "Automatic Date and Time" and "Automatic time zone"