Permanent multipliers obtained in multi crates while having that rank, which in that case you're platinum it doesn't stack. You already have platinum it will not combine to perm multipliers in the multi crate or the perks from bedrock > elytra. That would be too OP. It doesn't work like that.
You can only stack them by voting, buying/getting temporary multipliers, global multipliers, and the quest: 2000 blocks mined needed (only this because the other quests don't stack with other multipliers that you already have).