Most surely is this (transient) problem: a new version was released for that snap, but still not verified, and (because of a bug) we’re failing to serve it properly.
The latest core snap in stable hasn’t yet been validated for the Gateway 5000. It’s expected that this will happen first thing tomorrow. As Facundo mentioned, there’s a bug that’s being worked on which causes the error message when snapd tries to download an older version of a snap that is no longer published in an accessible channel. Once the latest stable core snap is validated for the hardware, the error will no longer happen and the core snap will be refreshed.
If you’d like to install now, you can do so using this command:
Facundo’s fix for this was rolled out a few minutes ago, so these devices should now happily update to the most recent, validated revision (which may not necessarily be the latest uploaded) . Could you please check and let me know if things are OK now?
I think you are mixing up version numbers for snapcraft (the tool used to create snap packages) and snap/snapd (the daemon and cli that manages the system).
The latest release of snapcraft is 2.33
The latest core snap on the stable channel for Gateway 5000 should bring you snap/snapd versions 2.26.14