Igor Pro V8, Windows, and default application for pxp files

I recently upgraded my Microsoft Surface 4 to IGOR V8. After having done so, I saw that my Igor pxp files were no longer associated with IGOR as the default launch application. I have tried setting IGOR to default through the "properties" window for pxp file as well as through the Windows 10 "Default Apps" window accessible through "Settings"...no luck. Through Google I found that this type of issue has arisen for other people using other applications. The general cause usually seems to be something about new software installations, changes to drive names or partitioning, etc. leading to Windows "losing" the path to the application or becoming "confused" because there are references to other paths somewhere in registry. Naively, I went to the registry and searched for keys referencing IGOR V7 and deleted them when I felt it was safe to do so. Again, no luck. This isn't a major issue since I can always start IGOR and then just open the file, but it would be nice if there was a simple solution that someone who may have also encountered this problem has discovered.