Hi,
The plugin is made to accept a relative path for the CSV file.
So the file should be in your Joomla folder.
Now I created a ticket in order to let the rest of the HikaShop team take a look more deeply in that plugin code.
I am personally not found to always convert the file path into an URL.
If you still have some issues with the plugin, please try to put a full URL like
http://www.mydomain.com/folder/import.csv
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.