Until recently, when I clicked on a drawing file in an inbox message (PDM Standard), or double-clicked a file in the vault, the file opened in a new window in Solidworks.
After a brief flirtation with SW2019, SP0, I uninstalled 2019 and, now, when I go to open another file as described above, a new instance of Solidworks opens.
I have tried Option, File Explorer, Restore File Associations. No change.
I suspect (I'm not sure why) that it has something to do with file associations, maybe SW files being associated with Solidworks, rather than with Solidworks Launcher, but that is a guess. Anyway, even if I'm right, I have no idea how to change it.
Windows 10 Pro