Hi i bought a key from Kinguin and the code is invalid,
They told me that the key works and contact GOG because maybe is a server problem and try to activate it, I wrote to the support of GOG and after 4 hours of waiting still no answer,I have to worry? Another question,they contact me from email? Because i don't find my ticket on my account

You'll get an automated e-mail. It's Sunday, no one's at work at GOG support.
They'll probably pick it up tomorrow or Tuesday.

Did you follow the activation instructions to the letter? Kinguin instructions:

Activation Details

In order to activate the key please follow instruction below:

Enter your coupon code and date of birth here.
Agree to the terms and conditions.
You will now be requested to log into your GOG account. You can register one here. This is a mandatory step, as your game will be automatically credited to your account at the end of the redemption process.
Click the ‘Sign in with GOG.COM’ button.
You will be redirected to GOG.COM sign-in page. Enter in your GOG.COM account email and password.
When logged in, you will be asked to allow NVIDIA access to your username, email address, and avatar. Click ‘I AGREE’.
You will now be redirected back to the redemption portal.
If successful, you should now see your GOG.COM username and avatar. Confirm this is the account that you want to claim against. If you have made a mistake, click cancel to restart the process, otherwise click continue.
Enter in your additional information (name, email address) and whether you want to subscribe to the GeForce Newsletter, and click redeem.
The game will be automatically placed in your account. If successful, you will see a success message and a link to your GOG.COM account.
You will also receive two emails – one from us, containing confirmation of the redemption, and one from GOG.COM as a receipt of the game being applied to your account.

The coupon is invalid when i enter my code of The Witcher 3