must have a matching product or they get an error message

1.

Looks like an HikaShop message regarding his coupon system and not an HikaSerial message for the serial consumption.

Thanks I moved this post from Hikaserial category to here.
Can I edit this message to have a link or to say something like "return to products page and add the correct product"?

Hi,

Sure. All the text of the interface and the messages can be modified with translation overrides:
www.hikashop.com/download/languages.html#modify
Translations can contain links. However, if you want the link to be different based on the product, that would require modifying the code behind it and while it's possible if you're a developer and some free time, there is no easy way to do it.