plasma-discover on stretch does not notify upgrades
I installed Debian Stretch with kde on two laptops. On one of then, I
never get notifications when upgrades are available. On the other one,
plasma-discover works as expected.
On the problematic installation, when I know that upgrades are
available (because the same packages have been upgraded on the other
one), the plasma-discover icon remains hidden. If I click on the
icon or open the discover program, it tells me that the system is up to
date. It is only when I open konsole and do an "apt update" that the
plasma-discover icon notifies me of an update.
Any idea how I can fix that ?
I had no luck searching the web. I have tried to compare the lists of
installed packages on both machines but didn't find anything relevant.