Hello,
The "HikaShop > System > Plugins > New" interface list all available HIkaShop plugins (in the group "hikashop"), even the plugins which are not compatible with the multiple-instance system.
But if the interface show you that plugin ; it means that the plugin is also available in the Joomla > Extensions > Plugins interface.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.