There are two reasons why a Dynatrace Portal user account is be locked out:
Incorrect Login Information. After 5 attempts to log in, with the wrong login information, the account will be locked.
Excessive Logins. After the user attempts to login more than 48 times in 4 hours, the account will be locked. This typically indicates an automated login process, which is prohibited in the Terms of Service.
Contact Customer Support to unlock the accounts.