Message "Discount code already used"

-- HikaShop version -- : 2.6.1
-- Joomla version -- : 3.4.8
-- PHP version -- : 5.4.44
-- Browser(s) name and version -- : Firefox 44.0.2

Some time ago I imported some discount codes. Since then, when I want to create a new code I get the message like "Diskount code already used" but the code is created sucessfully. Also on editing I get this message except with the older codes before my imported codes.
What my I have done wrong?
Best regards

Hello,
Did you checked that your didn't set a value already used by existing discounts through your new discount's "Code" option ?
Can you tell me how did you exactly imported your "older codes" ?

I tried it with a new not existing code but got this message.
The first codes I created with hikashop. Some time ago I imported around 400 codes direct in the SQL database. Since then I have this problem.

Hello,

Difficult to see what happen, because it's impossible for us to recreate this bug from our side,
BUT you tell us that the discount is successfully created how did you check this point?

If you check in your php my admin maybe, you only see the "old" discount with the same code?
And so, the message error is quite normal,

Awaiting news from you!

Regards,

I checked the table xxxx_hikashop_discount and everything seems to be ok. I created a new code just hitting some buttons "kjhermnb83ghdkbd7" and searching the table for this code if there is one. If not, I created a new discount in hikashop with this new code and got the message that this code is already used. It is not a major error. The code and every entry I made is created sucessfully. I can live with this message but it is a bit confusing for other who want to create discount codes.

Hi,

That's really strange because we're not able to reproduce the problem on our end.