Some communities are not synchronizing on my own instance even though I’m subscribed.

Some examples:

• https://lemmings.world/c/gog@lemmy.world
• https://lemmings.world/c/php@kbin.social
• https://lemmings.world/c/gaming@kbin.social
• https://lemmings.world/c/gaming@lemmy.ml

Why is that?