MUSICxml import - strange file extension issue

I received a folder with 6 .musicxml files.
When trying to import them into Dorico 4, I could not select these files, they were greyed out. The filenames were something like 02_song 2.musicxml
I then tried to open the file from within the finder. I am on macOS 10.14.11 I selected the file and in the context menu “Open with…” tried to access Dorico, which was not offered as a suggested application. I changed the dialogue from “Recommended Application” to “All Applications” and that way forced Dorico to accept the file - which was then been imported into Dorico just fine.
Now the strange part. When I tried the same procedure with the other 5 files (importing from within Dorico) I noticed that the formerly imported 02_song 2.musicxml file had stopped being greyed out. What is happening here? After having “force imported” them into Dorico, the context menu had changed. Is there an issue with the file extension .musicxml?

Where’s the folder stored? Your desktop? Dropbox? I ask as I’ve spotted that Finder (at least on Catalina) doesn’t always know what to do with files in cloud storage that aren’t cached locally.

Hi Leo, the files are directly on my HD, in the Download folder.

What I can say for sure is that this is nothing to do with Dorico itself, but rather a function of the operating system. What I’m less sure about is what’s actually going on: but I think perhaps it may be the case that when you tell the Finder that a particular application can open a particular kind of file, the Finder might remember that and thus show those files as now being directly openable.

Sounds like an issue with your LaunchServices database.