Suggestions
Here are some ideas that may help:
Use the correct url. See above. Point Chrome, Safari, or Edge to your company's .io site (e.g., mycompany.nthround.io). Pointing to just nthround.io will not work.
Use the correct email. Type in the SAME email address that the company uses for you. Other email addresses will not work.
Unblock authentication@nthround.com. Some stringent email systems (notably me.com and mac.com) block authentication emails. As a work-around, please ADD authentication@nthround.com as one of your Contacts.
Allow cookies. To enable secure device authentication, make sure your browser is not blocking cookies.