New Norton Pop-Up Window - Need Explanation

I'm frequently getting this pop-up window from Norton:

A problem has occurred that needs your attention:

Norton Internet Security cannot be installed because you have another version of Norton Internet Security installed.  Remove the existing version, restart your computer and run this installer again.

Does anyone here have a clear understanding of what this Norton message is about?

My PC is running Win8.1 and NIS v21.7.0.11 (with over 550 days remaining on subscription).  Everything on my PC runs great, and I do not intend to install Win10 until next year.