Unwatched iCloud Sync Troubleshooting

Enable Sync

Make sure iCloud sync is enabled in Unwatched on all of your devices under Library → Settings → User Data → Sync via iCloud
Restart the app after turning on the setting

Make sure you are signed into iCloud with the same account on all devices. On iOS, this is the very top menu item in the system settings.
Make sure iCloud Drive is turned on. Go to the very top menu item in the iOS Settings (with your Apple ID) and then go to the iCloud tab. Make sure the iCloud Drive option is enabled.
Make sure Unwatched is enabled in iCloud. Go to the very top menu item in the iOS Settings (with your Apple ID) and then go to the iCloud tab. Scroll down, find Unwatched, and make sure it is enabled.

To keep your data, back it up via Library → Settings → User Data → Backup Now. You can limit the size by excluding unimportant videos or disabling keeping all watched videos.
Delete both apps and Install the latest version on both devices
Enable iCloud sync on both devices under User Data → iCloud Sync. After enabling, force quit and relaunch the app.
Do not restore from backup yet. Manually add one subscription (e.g., via the in-app browser) on one device. A cloud symbol should appear next to the reload button.
Keep both apps open and allow them to sync. You don’t need to force quit or enable/disable sync; simply returning to the home screen and reopening the app can encourage syncing on the second device.
Refresh the app and see if the inbox/queue entries appear.
If the sync works, feel free to restore from your backup on one device and wait for it to sync to your second one.

Turn off iCloud for the App:
- Open Settings on your iOS device.
- Tap your Apple ID at the top.
- Open iCloud > Show All under "Apps Using iCloud."
- Find the app and toggle it off.
Delete the App:
- Go to Settings > General > iPhone Storage.
- Wait for apps to load, select Show All, then find the app.
- Tap the app and select Delete App.
Repeat on All Devices:
- Repeat the deletion steps on all devices using the app.
Reinstall the App:
- Download and reinstall the app from the App Store.
Turn iCloud Back On:
- Go back to Settings > iCloud > Show All.
- Find the app and toggle iCloud on.

This will ensure all app data is deleted from iCloud and the device.