If the USB cable can detect the Xiaomi 14T but does not allow access to its contents, here are some steps you can follow to troubleshoot the issue:
1. Enter [Settings] >> [About phone] >> tap [OS version] 7 times to enable [Developer options], then go to [Additional settings] >> [Developer options] >> [Default USB configuration] >> check if [No data transfer] is selected;
2. Please use the official data cable first;
3. Please change the other USB port of the device to connect the data cable;
4. Reboot the two devices;
5. Check for system updates. Make sure your Xiaomi 14T is running the latest version.