Theia Message Toast not showing

Hi,
I would like to display a message from a react functional component.
I injected the message service as in the docs to a widget:

  @inject(MessageService)
    protected readonly messageService: MessageService;

And I added the MessageService to the Properties Interface of my component.

If I use the messageService, the message is not displayed.

this.messageService.info('Hello World!')

What could be the problem?

Some other isses:

The documentation for TypeDoc of MessageService is not existing (404), where can I find those? (https://eclipse-theia.github.io/theia/docs/next/classes/core.messageservice-1.html#showprogress)

Is there an example for a custom MessageClient?

Kind regards, Knut

[Fixed]
If you struggle with the same problem: In my case I forgot to add “@theia/messages” : yourversion,
to the package.json.

Make sure that messages has the same version as your version of @theia/core, else you may run into this problem: https://github.com/eclipse-theia/theia/issues/7390

The documentation for TypeDoc of MessageService is not existing (404), where can I find those? (https://eclipse-theia.github.io/theia/docs/next/classes/core.messageservice-1.html#showprogress)