Greetings josejr1104,
We understand that when attempting to charge your Smart Battery Case while connected your iPhone, the case shows there is zero battery remaining and that it isn’t charging.
You had mentioned that this only occurs when your iPhone battery is already at 100%. Let’s be sure we’re covering all our bases and isolating the issue.
Does restarting your iPhone change the situation at all? Restart your iPhone
How to restart your iPhone X, 11, 12, 13, or later
1. Press and hold either volume button and the side button until the power-off slider appears.
2. Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force restart your device.
3. To turn your device back on, press and hold the side button (on the right side of your iPhone) until you see the Apple logo.
Is your iPhone up to date with iOS 16.1.1? That can be verified in Settings > General > Software Update.
Update your iPhone or iPad
Lastly, is the battery case charging your iPhone?
Thanks.