[KB872] I receive the error message "Serial number or Activation key already activated" or "Serial number exceeded the allowed number of activations"


  • You receive an error message when attempting to activate a serial number or activation key on the ESET website

About activating:

  • You only need to activate your activation key or serial number once. Whenever you reinstall your software, or install it on a new machine, make sure to activate using your username and password or License Key.

  • Activation issues are often due to expired licenses: When does my ESET home product license expire?



If you are receive either of the error messages shown below (see Figure 1-1) while activating on our website, you have already activated your activation key or serial number and received a Username, Password, and/or License Key via email. 

Figure 1-1

You now need to activate your ESET product. To do so, follow the steps below:

  1. Upgrade to the latest version of your product.
  2. Activate my Windows home product using my Username, Password, or License Key.

  3. Verify that your ESET product is updating correctly. How do I know ESET Smart Security/ESET NOD32 Antivirus is updating correctly?

I don't have my license information

If you do not have your Username, Password, or License Key, click here to have your license information resent.

If you are receiving the error message "The serial number you entered could not be found in our system" (see Figure 1-2), it is likely you entered your serial number incorrectly.

Figure 1-2

When entering your serial number or activation key, use the following guidelines:

  • Any hyphens ("-") in the serial number must be included

  • The serial number must be entered with no spaces

  • Verify that the letter "O" was not typed instead of the number zero

If you are still unable to resolve your issue, contact ESET Technical Support.