One USB-C port not working on my MacBook Air

Sounds like a hardware issue with that USB-C port. FYI, it is very hard to detect some damage to the contacts within the USB-C port due to how narrow the opening is. I've gotten pretty good at detecting physical issues, but there have been times the issue could not be seen until I physically removed the USB-C port from the computer (I am a hardware repair tech). Sometimes the issue may be with the Logic Board if the USB chip on the Logic Board has been damaged or has failed.

You will need to have Apple or an Apple Authorized Service Provider examine the laptop to provide you with a repair estimate. Everything you have described is what can happen when the USB-C port has a hardware issue. You've done a great job of troubleshooting.

Make sure to get a good backup of your computer now while you still can since Apple could erase the internal SSD during the repair.....if the Logic Board is replaced, then your data is gone since the SSD is integrated onto the Logic Board. I hope you already have frequent & regular backups since there are a lot more new ways to permanently lose access to the data on the internal SSD due to all the hardware, software, and security changes.