confirmed, updates worked after a retry today.
Suggestion: next time, use an HTTP error code appropriate for the situation, and allow the server response to influence the UI result. For example, in this case you could have used a 204 (no content) or a 503 (service unavailable) to indicate that the client request was OK, but the server was not giving out update info. Response body could be passed directly to the UI message, e.g. with a 5xx, you could show "failed to check for updates: update service is temporarily paused for a rollback. See shelly.support.eu for more information and try again later ", of which the majority is in the HTTP response body of the 5xx.
Anyway very happy to have the service back. Thank you for your hard work in what must have been a rough 24 hours!