Hi there,
It's important your new users are able to login. Don't worry, I'll be happy to give you a hand with this.
First, I'd like to start by doing some troubleshooting to determine if this isn't a browser related issue. When was the last time you cleared cache and cookies on your browser? Doing this will help fix most issues the site may be having. Here's an article which shows you how to do that: How to clear Cache and Cookies. Give this a try and if you're still having issues, I recommend contacting our support team using this link.
In the meantime, here's a helpful article with more info on adding users in QB Online: Add Users in QB Online.
