I was able to solve this by starting over basically. I went to App Store Connect and chose the new Xcode Cloud link. Then chose Settings on the left. And "Delete Xcode Cloud Data" and chose to delete. This seemed to delete my workflows for me as well. I then set up a new workflow again and this time I chose to go ahead and start a build when the screen gets to the "finished setting up a workflow would you like to start a build" and gives one option to select a branch. (The first time setting up I think I chose to not build at this time) Not sure which one of my steps above fixed it, but It can now detect my 'main' branch.