Can't download my older version of photoshop elements on new laptop: "Install needs to be updated"

I have an old version of Photoshop Elements 15 on a CD that I bought several years ago.  (I know, I know -- it's old -- but it still works just fine for me and I don't have any reason to pay for a brand new version of Elements when I already have this perfectly good version I paid for before).  I recently got a new laptop which doesn't have a CD drive, (and I am having problems getting my external CD drive to work with this new laptop for some reason), so I went to the forums and was directed to go here, https://helpx.adobe.com/download-install/kb/downloaded-older-app.html, to download it.  Fortunately it looks like I had registered my copy of Photoshop Elements to the Adobe website when I bought it, so the serial number was saved there.  I selected Photoshop Elements 15 for Mac and downloaded it, which seemed to work fine.  But when I try to open the installer that downloaded, it says this: "'Install' needs to be updated.  The developer of this app needs to update it to work with this version of macOS.  Contact the ceveloper for more information."  So it sounds like it's not necessarily a problem with this older version of Elements not working on the new laptop (that's yet to be seen), it's the installer that's not working.  Any chance anyone knows a workaround so I can keep using the version I already have?  Thanks!