Please check that iCloud Drive and iCloud are both enabled. Go to system Settings → Your name → tap iCloud → iCloud Drive. Please check that Collections is enabled in system Settings → Your name → iCloud →Show all.
Also, update the iOS or macOS app to the latest version.
Synchronization could take a while to complete, especially opening the app for the first time or importing large amount of data from a CSV file.
Please keep the app opened until synchronization is completed. You can monitor the sync process in Settings → Synchronization.
Please restart your device and restore the purchase from Settings → Restore purchases.