My 13” MacBook Pro 2020 Thunderbolt port not working/charging
I bought this brand new MacBook Pro few weeks ago, now one of the two Thunderbolt ports are not working.

Return it. Charging (I’m not referring to “Battery Health Management) is not something that’s regulated by the OS. It’s something that’s handled by the charger and the USB controller that negotiates charging current (you don’t boot the Mac to charge it).  I was recently reading a tech article where one one these controllers can fail for one port will “kill” the charging for all ports (have to find the article).  Could it be this?  Possibility or possibly not. Point is, you have a hardware issue that’s not going to be fixed by OS tweaks, unfortunately.
Given that this is brand new and you’re already running into issues, you need to return it. Not for repair, mind you, but for refund/replacement. It’s unacceptable that new products fail this suddenly. Don’t put the burden on your shoulders; put it on Apple’s (my consumer advocacy side coming out).