Hi,
The "product tag" plugin is not compatible with the front-end.
The link which does not exist couldn't exist because it use a special feature of the backend which is not available in the front-end.
So there is a bug in the plugin which shouldn't be display in the front-end (or the missing "plugin-trigger" feature should be added in the front-end).
I have create a bug report for this.
Sorry for the inconvenient but this button could not work in the front-end.
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.