How to restore inactive monitor turn-off?

[joe at actionline.com]

On my Linux Mint KDE system, after a recent update,
the monitor no longer turns off after 10 minutes of
inactivity like it used to. Now, the screen just goes
darker (not off) with the cursor arrow still appearing
but the screen stays warm, so no power saving. Why?

Under system settings > power management, I had:
[x] dim screen after 5 minutes
[x] Screen emergu savomg after 10 minutes
and I just added:
[x] Suspend session after 10 minutes

But the same problem continues with the monitor
failing to go "off" as it did before the update.

What do I need to do to restore the screen suspended/off
after 10 minutes of inactivity the way it was before the
last update?