Try verifying that the files are actually synced to iCloud Drive by visiting it on the web here: iCloud Drive
If you can see your synced files both there and on your Mac, make sure you are looking in the correct folder in Files on iOS. Files lets you access files and folders stored directly on your iPhone as well as those on iCloud Drive.
To make sure you're checking your iCloud Drive, tap Browse when you open Files, then tap the iCloud Drive location in the list. It might be that you were checking "On My iPhone" or in another cloud provider instead of iCloud Drive. Also make sure you're looking in the correct folder within iCloud Drive to find your files.
If your files are not visible on iCloud.com, how are you seeing in your Mac that the files have been synced?