Problem Reinstalling Photoshop Elements 14 on desktop

I had to temporarily remove my Photoshop Elements 14 software from my desktop computer about a month ago and have been trying to reinstall it using the CD I purchased from Best Buy years ago.  After installing, it initally told me that I had the software installed on too many devices, so I was blocked from using it on the desktop.  *But I do not have it installed on any other devices.*  (I  did at one point have it on a laptop, but have had it uninstalled from there for some time.)  Given the message, I uninstalled it from my desktop and tried installing again.  This did not help.  On this next reinstallation attempt, it kept getting stuck on "initializing installation", then eventually (finally) told me that installation failed because the software is "not genuine".  You can't tell me that suddenly now Best Buy sells non-genuine software or that Adobe is only just now detecting something "wrong" about it seven years later.  I then attempted to download the software from the internet and chose Photoshop Elements 14.  I was able to get to the point of putting in my serial number again, but now it tells me the serial number is invalid.  I'm typing it correctly, and it's the same one I've been using for seven years.  Why is it invalid now?  Whether or not the product is "outdated" and no longer supported, the fact remains, I purchased it, and I should still be able to use it with the serial number I was provided when I did so.  Any help with getting this situation straightened out, helping me to be able to use this software again, that I have relied on, would be greatly appreciated.  Thank You.