My experience with similar errors is that this is usually caused by opening the wrong parent folder and the vex extension not recognizing it as a project. Are you sure you are opening the correct folder?
Just to preface this, I’ve never used the vex robotics extension on vs code, ive always used pros. I hit command B (thats what my sister team said to do) and nothing happened at all. It didn’t download.
Did you open the folder directly, or use the import feature of the extension? You need to use the import button and click on the .v5code file for it to work.
Do you have clangd installed or the Microsoft C/C++ extension? PROS uses clangd but the vex vscode extension uses the Microsoft one. If you want to use clangd with the vex vscode extension you will need to create your own configuration file so I recommend just uninstalling clang and using the Microsoft extension instead.