The different answers here are based on two different install methods and habmin has to be installed in different folders based on the chosen install method:
Manual install:
1a) manual install of openhab:
the tutorials recommend to copy the downloaded files in
/opt/openhab
The addons folder for ALL addons is /opt/openhab/addons
1b) habmin based on manual install:
extracted habmin.zip goes to
/opt/openhab/webapps/habmin/
zwave and habmin jar go to /opt/openhab/addons
apt-get install
2a) apt-get install of openhab:
this creates a completely different folder structure, there is NO /opt/openhab folder
Instead you have (among others) for ALL addons:
usr/share/openhab/addons
2b) habmin based on apt-get install:
extracted habmin.zip goes to
/usr/share/openhab/webapps/habmin
zwave and habmin jar go to
/usr/share/openhab/addons
If you have mixed these two different install methods it won’t work.
Easiest way is to start from scratch …