This information can help you if you mis-type your password to often and get blocked by the USG.
Step by step procedure
You can use the following CLI command to unlock the source IP address via console or SSH.
Router# show lockout-users
Router# configure terminal
Router(config)# unlock lockout-users W.X.Y.Z
Then the IP address W.X.Y.Z will be unlocked in the list.
You can try the password to authenticate with the device again.
After unlocking the address, you will be able to log in to the device again.