i think a given observation must reach research grade before it’ll automatically affect the place checklist. since you haven’t provided your specific observation and place, it’s not possible for me to check whether your observation has reached RG, but that’s what i would check first.
that said, place checklists are very old functionality. they are known to be buggy, and they are supposed to be replaced (similar to how the old user checklists were replaced with the dynamic life list) soon. see this thread for more discussion: https://forum.inaturalist.org/t/place-checklist-doesnt-show-all-research-grade-species-observed-in-that-place/11609.