sounds like a sync issue. federated links don't direct you away from your instance so you can actually interact with the communities being linked to no matter what activity pub software you're using.
Lemmy users have a bad habit of using local links which are next to useless unless you're on the same instance.
! is a lemmy thing and sends you to the original url, @ is a fediverse thing and sends you to the linked community on your own instance so you can actually interact with it.
Nothing like shitting on people for not knowing how federated links work, then posing community links as user links. I would link to the selfawarewolves community, but fuck ml. Anyway: