Sounds like you either installed a corrupted version of WB, sometimes a download process can corrupt a file if there are network issues. Seems unlikely to me, but I suppose that it ca happen on rare occasions. More likely there may be a conflict between Windowblinds and another piece of software on your system, and the conflict is creating that issue and popup.
Have you tried just shutting down the pc, and then rebooting up again? Sometimes just a shutdown and reboot can help....
If not, please try this: Here the steps on Windowblinds purge and reinstall
https://forums.stardock.com/486023/windowblinds-support-faq#reinstalling.
Again, just to make sure re-download latest Windowblinds from your account. Reboot after the purge. Reinstall Windowblinds. Reboot again after the installation. Retest to see if the problem still there.
Report back here and let us know if you are still having issues!
