Mastodon not federating to Lemmy?

I’m not sure if this is the wrong place to post this; my apologies if it’s not.

Anyway, I have an inquiry about Mastodon replies seeming to not post to show up on Lemmy.

Earlier today I made a post on Mastodon and made it post to Lemmy as well, by @ing the community I wanted it to appear in. Here’s a link to the post on Mastodon, and here’s how it showed up on Lemmy. At first, everything seemed to work fine.

But something I noticed is that, though the Lemmy comments were visible to me on Mastodon, the reverse was not true: most of the Mastodon replies were not visible on Lemmy. So there seems to have been some federation issues there.

So my question is, does anyone know what caused this and if so how I can fix it?