If you’re having problems after you’re certain that you are inputting the correct username and password in an UnixWare like in this case below

emerson@shellcore:~ $ telnet 192.168.45.54
Trying 192.168.45.54…
Connected to 192.168.45.54.
Escape character is ‘^]’.

UnixWare 2.1.3 (SCO) (pts/0)

login: emerson
Password:
UX:in.login: ERROR: Login incorrect
telnetd: Unable to invoke login scheme.
Connection to 192.168.45.54 closed by foreign host.

You need to clear the file /var/adm/lastlog

root@SCO:/ # > /var/adm/lastlog

After that, you’ll no longer see the message that is preventing you from logging in

emerson@shellcore:~ $ telnet 192.168.45.54
Trying 192.168.45.54…
Connected to 192.168.45.54.
Escape character is ‘^]’.

UnixWare 2.1.3 (SCO) (pts/0)

login: emerson
Password:
UX:in.login: ERROR: Your password has expired.
UX:in.login: TO FIX: Choose a new one
Old password: