Hello,
I've tried to install JoomSEF 3.2.11 (Joom! 1.5.9) but have the following problem -
After the installation I get the message

JoomSEF plugin not installed. Please install it manually from the following folder: ....../httpdocs/administrator/components/com_sef/plugin/

but right under this message is another: Installation of the component Success.

So is it installed properly or NOT?
How can I istall it manually? What files and where?

I can start JoomSEF, but it is not working properly. In Global setting usually only left part menus are available. Menus on the right are not visible. I cannot save settings, exit setting :(
In 1 of 5 attempts also right menus are visible and saving and exiting the global settings menu is OK.

.htaccess was changed accordingly, SEO/SEF and mod_rewrite is set to Yes.
Thanks for any help.

Hello,

this error means the plugin was not installed (the component installation went through fine). Plugin is neccessary for correct functionality.
I would recommend you to ensusre that folders /plugins and /plugins/system are writeable and then reinstall JoomSEF once egain.