Why doesn't password plug-ins work

[ziluopao]

I used the Roundcube Webmail 1.3.3. After installing the password plug-in, I tried it and found it was not available.
The error message is shown in the figure
The log of the plug-in is such a reminder

[04-Dec-2017 11:12:46 +0800]: <967hlgfa> DB Error: [1305] FUNCTION roundcube.update_passwd does not exist (SQL Query: SELECT update_passwd('$1$3kVAvBdMO$5ZHtcS79artzGKfgO4Qt6/', '[email protected]'))
  in /www/wwwroot/webmail.jnjad.ml/program/lib/Roundcube/rcube_db.php on line 543 (POST /?_task=settings&_action=plugin.password-save)
What am I going to do！Help me!

[SKaero]

You need to configure the password plugin, read the README file in the password plugin folder.

[ziluopao]

Sir,After I read README, there are some questions, please answer, thank you!
The FUNCTION update_passwd(hash text, account text) should be in which document.