This article applies to our on-premise products, Paessler PRTG Network Monitor and Paessler PRTG Enterprise Monitor. 

If you receive a License not found error message in PRTGit is most likely one of the following: 

  1. (1) An error in the entered license key. It is possible there is a typo in the entered key. Double check the license key with the license document you received with your last purchase and try again. We recommend that you copy and paste the license key directly to avoid typos. 

  1. (2) Your PRTG version is too old. Your license key might not be compatible with your installed PRTG version. In this case, you must update to the latest version. Follow the steps to update provided in the email that your license key came in. 

For more information, see the PRTG Manual: Update from Previous Version. 

If you still need assistance, please reach out to our Customer Service team via