App Center: "Unknown Snapd Exception" (what does it mean?)

I’m getting this: cannot list updates: cannot query the store for updates: got unexpected HTTP status code 503 via POST to “https://api.snapcraft.io/v2/snaps/refresh

It’s kind of cryptic message
snap_exception
and the updating of apps via App Center mechanism does not work.

I received a similar message using the command-line tool, but now it seems to work again.

Any time there’s an error in the 500 range it means it’s a server side error and that it’s on the server end, not the client end, and there’s nothing you can do but wait. It’ll resolve itself.

Please, in the future, do not ask for help in such a way in this discourse as it’s not set-up in such a way (it has different goals). The Finding Help topic details where you can get support.