Please make sure you have "undetermined" selected in your list of spoken languages in your lemmy settings in addition to any other languages you speak.
Most lemmy content does not come through with a language tag, and you need to have undermined selected as an option to see that content.
Thanks, that makes sense. It would be nice if there was at least a way to prompt the server to refresh comments on a particular post or community.
(I did figure out that you can force it to see a particular comment by searching the URL of that specific comment, which is useful in cases where there's something particular you want to reply to and you already know that it exists.)