Hi,
I understand your request but in the other hand, I didn't add that message for a very specific reason : security.
Displaying a message to indicate the reason why the consumption is not made can give indications to the end user for some elements which he shouldn't know.
That's why a user won't know if a serial exist or not, he won't know that the serial is entered is assigned to someone else, that he does not have the right to perform the action, etc. It is security purposes !
I can see to add an option in the plugin instance configuration. So when you add a group filter, you could authorize the display of a message.
But I won't add that kind of message by default for everybody.
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.