Are you using a different client by any chance #[1] ?

I have been trying Iris, Damus, Snort and another one. I've found that depending on which nostr relays they are connected to, you'll have different results. Each relay holds a copy of your data, if it only makes it to one and the other clients don't have access to that one, you won't see it elsewhere.

There is a short explanation halfway down this page - https://usenostr.org/