User unable to sign up account


Hello, I have a few users (one from Canada and 2 from China) who are unable to sign up with Smartsheet. They are not able to click on "Continue" and it is greyed out. Here are the screenshots they've provided below. I've re-prompted the user signup invitation and use a new invitation link but they're still running into the same issue. I've also asked them to use Google Chrome and Firefox and that has not helped either. What can I do to resolve this?