The Following document say "All accounts include a lockout mechanism. If the system detects a quick succession of multiple failed login attempts, the user account is temporarily unavailable to prevent brute force attacks."
How many failed login will an account be temporary unavailable?
If account is unavailable, what should I do in order to let account available?
I moved this as I think we need a Marketing Cloud expert to comment.
Normally the account will auto unlock after a set period. It is likely that a manual password reset will achieve an unlock also