RingCentral DevTest Web Page doesn't work

Hello everyone, I'm developing a app with RingCentral widget, when I try yo use it I have an error, so I searched for information and that happens because I don't have a digital line is associated in sandbox, I follow up the instructions at https://support.ringcentral.com/article/ringcentral-phone-softphone-outbound-calling-adding-digital-line.html?language=en_US

It's says that I need to enter on the website https://service.devtest.ringcentral.com/ to do the process, the problem is that the site doesn't works, it gets stuck too much, many times it doesn't load, and any link, thing or menu where I click on gives me a request error and doesn't let me move forward, I've been trying to do it for several days but the page doesn't work at all.