Hi Paulo,
found some time to reproduce your problem.
This code works without any problem here:
String uri = "https://www.easynvest.com.br/autenticacao";
try (final WebClient webClient = new WebClient(BrowserVersion.FIREFOX_60)) {
webClient.getOptions().setUseInsecureSSL(true);
HtmlPage page = webClient.getPage(uri);
webClient.waitForBackgroundJavaScript(5000);
System.out.println("----------------");
System.out.println(page.asText());
Might be that the reason is fixed in HtmlUnit or the page has changed.
Unable to download JavaScript from 'https://www.googletagmanager.com/gtag/js?id=UA-53783619-9' (status 503)
means, the server is not able to respond to your request.
Please open a new issue on github if you still have this problem.