Thanks for responding KevinM82,
And thank you for providing more context. It seems that the issue might be related to the Wallpaper Engine app's compatibility with the Lenovo Tab P12's PC mode and lock screen.
Unfortunately, not all apps are fully compatible with every device's specific features. It's possible that the Wallpaper Engine app may not support video wallpapers on the lock screen or PC mode screen of your Lenovo Tab P12.
I recommend reaching out to the developers of the Wallpaper Engine app for further assistance. They might be able to provide a solution or update the app to support these features on your device.
For now, I would suggest you to continue using wallpaper(s) on the tablet via the default Wallpaper settings itself.
Regards,
Adriel_Lenovo