After a user enters their password incorrectly six times in a row, their account gets blocked. This is a security precaution against cyberattacks. When blocked, users cannot log in to the panel with their One-Time Password (OTP) or regular password.
Before the sixth attempt, the user sees a warning message as shown below:
After the sixth attempt, the user is temporarily blocked for two hours. They need to check their email address.
To log in, they will receive an email to reset their password. 
To reset the password, they click the Reset Password button. Then, they can set their new password to log in.
When all is set, the user can log in to their account successfully.
If the user is locked three times consecutively, the account will not be opened for security reasons. You should contact the Insider One team or create a support ticket.