I recently wrote a whole article on how I use Cloud Battery which you can check out below.
There was a time when you could track AirPods and other peripherals on Cloud Battery, but it was being obtained through a method that is not meant to be used as a 3rd party developer. Since this was the only way to get AirPods battery data, you can no longer track AirPods battery in Cloud Battery.
Cloud Battery requires you to enable iCloud Drive within the iCloud settings, and also to enable Cloud Battery to store in iCloud.
It is likely you are not connected to the internet, or have a slow connection, so iCloud cannot be reached.
There can be many reasons for this, but the most likely is that iOS has not given Cloud Battery a chance to run its background refresh cycle. Keep in mind things like Low Battery mode almost completely block background refresh. There are many ways to improve this, adding iOS 14 home screen widgets make a huge impact and can help immensely to solving this issue, as well as the Today Widget. Using the Watch Complication allows the watch to update 4x more (every 15 minutes) than without it and personally I have found the Watch Complication makes a huge difference. The Big Sur widget allows Cloud Battery on the Mac to run without having the app open. The real game changer for me has been using Siri Shortcuts to automate syncing when my battery falls below important thresholds, which I talk about below.
Go to the today screen by swiping left on the home screen, scroll down to edit, and you can add the widget there! To add the iOS 14 widget click the plus on the widget screen! There are also macOS Big Sur Widets and Today Widgets available.
Try clicking the reset button in the add panel, that should fix things!