Depends on the PAM configuration on Linux server, the Pluggable Authentication Module (PAM)

To check the login attempts to see if it needs to be reset type faillog -u <username>

root@testsrv:~ # faillog -u user1
Username Failures Maximum Latest
user1       15        0

Reset the counter with the -r flag:

root@testsrv:~ # /usr/bin/faillog -r user1
Username Failures Maximum Latest
user1        0        0

If you’re root but is not managing to become a user with su, you also need to reset the login counter:

root@testsrv~ # su – username
su: incorrect password
root@testsrv:~ # /sbin/pam_tally —-user user1 —-reset
User user1 (672) had 34
root@testsrv:~ # su – username
user1@testsrv:~ $