"Content Unavailable" message is presented when Files app access Drive resources on iPad

Remove the Google Drive App from your iPad. After deleting the App, perform a forced restart of the iPad:

Remove apps from iPad - Apple Support

Force restart iPad (models with Face ID or with Touch ID in the top button)

If your iPad doesn’t have the Home button, do the following:

1. Press and quickly release the volume button nearest to the top button.
2. Press and quickly release the volume button farthest from the top button.
3. Press and hold the top button.
4. When the Apple logo appears, release the top button.

Force restart iPad (models with the Home button)

Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.

After restarting the iPad, you can reinstall the Google Drive App from the App Store:

https://apps.apple.com/app/google-drive-online-backup/id507874739

When the Google Drive App has been installed, launch the App and sign-in with your Google account credentials - and verify that you can access expected files and folders within your Google account. If all is well, you can verify that the same files and folders can be accessed from the native Files App.

You're very welcome. I'm delighted that the problem was easily resolved.