Make sure to choose "Log in with a Work or School Account" at the login screen. Use your work email to log in, not a 3rd party email like Hotmail, Outlook.com, Gmail, Yahoo, etc.
Make sure to log in using the email address your invitation was sent to.
Your email address must be associated with a Microsoft Organization ID. If you use your account to log into a service like Office 365 or Power BI, you're all set. If you need an Organization ID, you can get one by signing up for a free Power BI account.