1. Check if battery share is enabled or not. Go to Settings>Battery>Battery Share> Allow Battery Share. Enable All Battery Share.
2. When Phone (1)'s battery is lower than the default limit in Settings, it will stop sharing power. Go to Settings>Battery>Battery Share> Allow Battery Share. Please enable All Battery Share. On this page, you will see the default settings is "Stop sharing battery when phone reaches 15%."
3. Remove Phone (1)'s case and other items that can cause interference, like metal objects.
4. Make sure both devices are in correct positions during battery share.
5. Check for device compatibility.
If you still can't sovle your issue, please contact Nothing customer support to assist you further.