I've seen an issue recently where behavior packs and resource packs will not load for players who join my world despite turning on "Require players to accept resource packs". Normally the behavior pack and resource pack are auto downloaded when a person joins while that feature is enabled.

Reproduction steps: Create a new world with a resource pack and behavior pack attached to it (doesn't matter which one so long as it isn't just the default packs that Minecraft uses), Then turn on "Require players to accept resource packs" and tell a friend on console or anyone who doesn't have the pack to join.