Re: Key 'gateway' not found in connection profile.
Hi @Anonymous,
Have you tried creating a File system connection in Flow-connection?
I have made a test on my side and don't have the issue that you mentioned.

I didn't add a connection in the Power BI admin center, but instead added a connection directly in Flow-Setting-Connection.
Make sure there is a File system connection in Flow connection list, and its status need to be Connected.
Besides, please update Gateway to the latest version, and Gateway needs to be used in the default environment.
Please take a try and see if issue still exists.
Best Regards,
Barry