Upgraded Packages And Ports, Can't Shutdown From Mate Menu Bar

[B J]

I just upgraded all the packages and ports on one of my machines.  It still
runs 12.0 under Mate.  The only glitch was when the package upgrade halted
due to, apparently, an attempt to install something from two different
sources in the same place.

I restarted the package upgrade and it continued from where it left off,
with no mention of the aforementioned conflict.

My question is how I can fix it so that I can shut down my machine using
the Mate menu bar.  I can shut it down from Terminal, using:

shutdown -h now

I don't recall seeing anything about this on the mailing list.

Any ideas?  Suggestions?  Thank you.

B. M. Jatzeck