Can't see a Sharepoint root folder for a channel

You most likely created a private channel. This doesn’t not put a folder in the same team / site library like normal channels and instead creates a hidden site and library separate from the connect site for the Team. The only way to find this is through Teams and the channels files tab.

If you want a folder on the team site then create the channel as a standard channel.

This is just an assumption but you can tell by checking the channel in your team and if a lock is by it then it’s private.