Must click TextArea for changes to appear. Why?

I have code updating a TextArea like this. Why do I need to click on the TextArea in the browser for the updated value to display? Even if focus is on the TextArea updates dont’ appear. A mouse click is required. Using Vaadin 8. Thanks!

ui = UI.getCurrent();
ui.access(() -> textArea.setValue(myString)); // this 

Do you have push enabled (
Server Push
)?

Yes, that was the problem. Thanks!