Hi, j.siebern.
When adding a user in QuickBooks Online, have them access the “Let’s go!” link when they received the invitation email. They'll be asked to sign in or create a new account.
If the user still unable to log in, let's perform basic troubleshooting steps by opening the link in a private browser. Here's how:
- Google Chrome: press Ctrl + Shift + N
- Mozilla Firefox: press Ctrl + Shift + P
- Safari: press Command + Shift + N
If it works fine using the private window, let them access the account using the original browser and clear the browser's cache. For your reference, you can go through this article: Add, delete, or change user access. It contains more details on how to accept the invitation as well as a brief video to serve as your visual reference.
Additionally, in case you want to learn what a standard user can and can't do. Here's a detailed look at the different levels of access in QuickBooks Online: User types and user permissions in QuickBooks Online.
Let me know the result of this troubleshooting in the comment below. I need to make sure this is resolved and you're able to add the user. All the best!