Enable the supported launch option in diCleaner Menu settings.
Then open System Settings → General → Login Items & Extensions and confirm the diCleaner component is allowed.
Sign out and sign in, or restart, to test. Do not keep duplicate app copies or login entries.
If the icon remains absent, open diCleaner manually and check menu-bar space. Organization policy can restrict login items.
Disable the option and macOS login entry when you no longer want it to start automatically. The main app remains available.