webmin-virtualmin-webserver not starting after linux-image and webmin upgrade


I made an upgrade of linux-image and webmin on my virtualmin control panel.
Webmin&Virtualmin and my web server are not working.
I tried with this command:

root@host ~ # /etc/init.d/webmin restart
Stopping Webmin server in /usr/share/webmin
cat: /var/webmin/miniserv.pid: No such file or directory
/etc/webmin/stop: 4: kill: Usage: kill [-s sigspec | -signum | -sigspec] [pid | job]… or
kill -l [exitstatus]
Starting Webmin server in /usr/share/webmin
Failed to open SSL cert /home/slo/ssl.cert at /usr/share/webmin/miniserv.pl line 4416.

Obviously I tried restarting the vps without results too.

root@host ~ # hostnamectl Static hostname: host.***.com Icon name: computer-vm Chassis: vm Machine ID: hide Boot ID: hide Virtualization: kvm Operating System: Debian GNU/Linux 9 (stretch) Kernel: Linux 4.9.0-8-amd64 Architecture: x86-64

What do you advice me to do?

Thank you very much