If Rust-Analyzer is not analyzing your code, that is you get no type annotations, no "Run" button and no syntax hightlighting then:
check that you have a single folder open in VS code; this is different from a single-folder VS code workspace. First close all the currently open folders then open a single folder using the 'File > Open Folder' menu. The open folder should be the
beginner/appsfolder for the beginner workshop or the
advanced/firmwarefolder for the advanced workshop.
use the latest version of the Rust-Analyzer plugin. If you get a prompt to update the Rust-Analyzer extension when you start VS code accept it. You may also get a prompt about updating the Rust-Analayzer binary; accept that one too. The extension should restart automatically after the update. If it doesn't then close and re-open VS code.
You may need to wait a little while Rust-Analyzer analyzes all the crates in the dependency graph. Then you may need to modify and save the currently open file to force Rust-Analyzer to analyze it.