Assuming this isn't a temporary problem with one of your provider's servers:
Sometimes for old files, providers may store articles in a slow backend and take some time to retrieve them; so in those cases an initial request may result in 430, but a later request will be OK. In any case, if this happens again, you could try raising retry count/time in Setup > Connection.
For newer files, it could be an issue with articles not propagating yet to your provider, or not fully across their whole server cluster. I'd guess in that case the provider forum/other users would have more info.