Please follow the below steps:
1. Please make sure you use the official Nothing adapter and charging cable. If using a different charger to charge, the software will recognise it as a non-standard charger and will limit the charging current, resulting in insufficient charging.
2. Try to replace the adapter and data cable to see if this affects the charging.
3. It is recommended not to use the phone while charging.
4. Restart the phone and try charging again.
If the issue persists, contact the Nothing Support Team for further assistance.