I have tried both methods but each time it offers Photoshop CC 2019, but it
just will not accept it and leaves the setting dissociated.
Looking in the registry under CR3, there is nothing in the folder.
I think I don't have the knowledge to change the registry, so I think I
will have to accept I can not do this
BUT
thanks for trying to help me.
I had exactly the same problem and I solved it by adding some values in the registry
I copied the keys and values under "OpenWithList" from the .cr2 entry to the .cr3 entry.


(The OpenWith.exe value was added by Windows.)
I can now open a .cr3-file in the Explorer or from within Bridge without having to select an app.
The files are not recognized as being image files by Windows, but that requires some update to Windows.