The information in this article pertains to an old version of PROKON that is no longer available.
After activating with a key disk created after 09/2002, an error 4 is generated on Prokon startup
With version 1.9 (post 09/2002) some changes were made to the licensing system that are not backward compatible i.e. new key disks will not activate versions lower than v1.9.
To fix this error simply re-install Prokon from the CD that you received with the key disk or download and install the latest service pack from https://www.prokon.com/downloads/servicepack.