There's a problem with some of the selected assets in both the template and the variant. Videos can't be processed until you've fixed all asset errors.
To fix asset errors in the template, click Edit template. You'll be taken to the Template tab where you can review assets with errors. Edit the asset outside Ads Creative Studio to fix the problem and upload the asset again or select another asset.
To fix asset errors in the variant, click Edit variant. You'll be taken to the Variants tab where you can review assets with errors. Edit the asset outside Ads Creative Studio to fix the problem and upload the asset again or select another asset.
If you need help fixing asset upload errors, go to Troubleshoot asset upload errors.