Posting this issue here as I think it applies to all Puppies.
The problem:-
If a user activates Xlock but closes the "Key (Password)" window without entering a password (not an unusual thing to happen), Xlock will then not open at all on subsequent attempts.
This is because a blank file gets created at /root/.xlockrc which prevents the program from opening because it expects this file to contain the encrypted password.
Deleting this file fixes it, but many users will not be aware of this.
There is a suggested fix by MochiMoppel here:-
viewtopic.php?f=63&t=3343
Looks like this would require an update to the package xlock_gui-0.2-7.pet in the pet_packages-noarch ibiblio repo. This seems to be the latest version of this package. Last updated in January 2020.