According to reports, Apple's new MagSafe 3 power connector can fail to charge the MacBook Pro 16 when the machine is switched off. Seemingly, the issue does not hinder the MacBook Pro 14, which also supports MagSafe 3.
https://www.notebookcheck.net/Reports-of-MacBook-Pro-16-charging-issues-emerge-using-Apple-s-new-MagSafe-3-cable.582199.0.html