Malzahn

Uninstall and reinstall worked for me, too. While working, this is not a satisfactory solution since I had to redo all the configuration. And as Cybertooth pointed out - let's see how long it lasts.

For clarification this was the status before trying marcos steps.

Hi @Marcos, Your previous suggestions didn't work for me or @Cybertooth as posted by both of us on Friday. We also could not completely execute them, since we don't have an esets_update program. Maybe these instructions are for a different linux software version (e.g. the buisiness version)? We also provided additional information on Friday in case they might be useful. Please advice how to proceed.

Tonight I went back to the computer and found the desktop very sluggish when not simply unresponsive. Clicking on items in the taskbar would either do nothing, or open the programs extremely slowly and then the windows would not finish opening.
I ended up doing a hard reboot, but just as I was releasing the power button I noticed that the ESET NOD32 Antivirus for Linux icon in the notification area looked red. After rebooting, the system works normally -- except that the ESET icon is no longer showing up in the notification area. And clicking on ESET from the Application menu does not open the GUI. However, I can see the ESET processes running in KSysGuard.
I am using Kubuntu 18.04 LTS with Plasma version 5.12.9. I think I am on ESET for Linux version 4.95, but I can't remember for sure and of course I can't call up the GUI to verify.
What can I do to get the GUI back? As a Windows refugee, I don't know how else I would make use of the program.
Thanks for any tips or suggestions.
 

I could not see a "modules" directory in /var/opt/eset/esets/lib/ . The only directory is data
Neither removing only the *.dat and files in /var/opt/eset/esets/lib/data/updfiles/ (one machine) nor removing everything in lib (other machine) resulted in success.
I do not have a /opt/eset/esets/sbin/esets_update file the only files in sbin are
esets_daemon  esets_scan  esets_set

Restarting with sudo systemctl start esets resulted in:
Job for esets.service failed because the control process exited with error code.
See "systemctl status esets.service" and "journalctl -xe" for details.
systemctl status esets.service resulted in:
● esets.service - ESET NOD32 Antivirus
  Loaded: loaded (/lib/systemd/system/esets.service; enabled; vendor preset: enabled)
  Active: failed (Result: exit-code) since Fri 2020-11-20 09:35:54 CET; 4min 41s ago
 Process: 4587 ExecStart=/opt/eset/esets/sbin/esets_daemon (code=exited, status=69)

Nov 20 09:35:50 mertins007 systemd[1]: Starting ESET NOD32 Antivirus...
Nov 20 09:35:54 mertins007 esets_daemon[4587]: error[11eb0000]: Cannot initialize scanner: Module init
Nov 20 09:35:54 mertins007 esets_daemon[4587]: error[11eb0000]: Cannot initialize scanner: Module init
Nov 20 09:35:54 mertins007 systemd[1]: esets.service: Control process exited, code=exited status=69
Nov 20 09:35:54 mertins007 systemd[1]: esets.service: Failed with result 'exit-code'.
Nov 20 09:35:54 mertins007 systemd[1]: Failed to start ESET NOD32 Antivirus.