Vaadin 19 UI access from thread

Migrating from Vaadin 14 to 19.

Added an AppShellConfigurator class:

package com.hpi.tpc.ui.views.main;

import com.vaadin.flow.server.*;
import com.vaadin.flow.shared.communication.*;

@Viewport("width=device-width, initial-scale=1")
@PWA(name = "TPC", shortName = "TPC")
@Push(value = PushMode.AUTOMATIC)
public class AppShell implements AppShellConfigurator {

I call a method from the UI with:


and that method uses:

private void download (UI ui){
final Double progress = (new Double(iRow) / (iTotalRows * 2));
	ui.access(() -> {

where PbProcessing is a progress bar.

This worked fine in Vaadin 14. Now, the progress does not show, much the same result as not having @Push enabled.

What am I missing?