I recall seeing a bug with Photos and switching between R+J when the RAW is unsupported. It definitely used to work, but it may hang now. That’s a Photos bug (the extension isn’t loaded, so it cannot be the extension causing the problem).
The key thing to know is that the extension is very restricted in what it can do. It can only edit the image that Photos gives it. In the case of R+J, it edits one or the other depending on the Use RAW Original or Use JPEG Original setting. The extension _cannot_ switch to the RAW on its own (there is no facility for that).
If you are set to JPEG+RAW (that is, viewing the JPEG), then that’s what Photos sends to the extension (only). If you switch to RAW, then it gets that (assuming you have not edited the image in Photos or another extension already).
You might have better luck if you switch to RAW before entering edit, but I don’t know for sure (I’m not at my computer to test this myself).
The standalone app has full access to both the R+J so it can edit either half of the pair as needed.