Hi
Until you get a better reply lets eliminate duplicated keyboard combinations please?
Menu -> Preferences -> kb shortcuts
so is it still C + A + l ?
Next, scroll thru all combos and make sure you have no duplicates
Next how many screensaver apps have you installed?
show results of
dpkg -l | grep saver
Next do a full reboot and do nothing about closing anything
or deleting anything.....unless you want mate-screensaver and have accidently installed another app.....
now run and post the results to this command.....as C + A + l works for me
but I am on 19.04...not sure if you will see the same result but I include it
/usr/bin/mate-screensaver
(my result)
** (mate-screensaver:4305): WARNING **: 10:20:08.284: screensaver already running in this session