I have problems selecting an output style outside the default output style folder location (even with the default folder location changed to the desired folder via preferences). The desired folder location is in a OneDrive folder, synchronized on different machines.
I would check with support, but I suspect endnote doesn’t know how to use onedrive for folder locations…
In my experience, EndNote doesn’t like having files in sky-services like OneDrive. In a similar case this week, the problem was solved after changing the style folder’s location to the hard-drive instead of OneDrive.