Primal's cache servers don't fetch everything. In fact, you could, sort of and kinda, say that Primal isn't exactly "in spec".

When you open Primal, it fetches events from it's cache servers rather than the individual relays - meaning, you only see as much as those cache servers catch. When you post, however, it goes to all the relays you configured.

This has the side-effect that you don't see all your follows in your feed. I have this problem on a regular basis with the bridged RSS feeds I follow. They all, entirely, do not show up.