When i try to add new plugins to my wordpress account i get this error:
"An Unexpected HTTP Error occurred during the API request."

Does this mean i can't use wordpress plugins on zymic hosting?
I have got a free account on zymic and i use Wordpress 2.8.6

Download a plug-in file to your PC and unzip it.
Using FTP, upload the extracted folders/files to your wp-content/plugins folder.
Activate the plug-in from 'Plug-in' admin page.

Unless the plugin uses a disabled command or tries to load content from another server, plugins for WordPress are allowed. Try what freescrapbook had stated. If that doesn't work, please come on IRC so a trusted staff can help guide you through a troubleshooting process.