Hi there, Martin!
Please note that by posting here, you are reaching out to the Kaspersky community and not to the official Kaspersky support
Reinstalling a product does not mean that you lose a license slot.
a. Log in to https://my.kaspersky.com
b. Go to Devices and click on your PC.
c. Under the PC screen image on the left, click on the link to disconnect your device.
That way the occupied license slot will be freed, and you can reuse it for the new installation.
The error you encounter seems to be related to your user account, which is (possibly) not an admin account for your PC.
In such cases, the program should be installed over an account with admin rights.
If that is not the case, please contact the support and send them a screenshot of the error and a gsi report.
Take a screenshot: https://support.kaspersky.com/common/diagnostics/492
Generate report: https://support.kaspersky.com/common/diagnostics/3632
Have a nice day