Raising this case on behalf of Ben from Hunt the Night.
Merchant is having issues with products approved for Shopify but not syncing to it.
Many examples can be found (at time of creating case) for the brands:
e.g : Product "9420030004051"
I have tried successfully to trigger a resync for 2 affected products by making a slight change to the Description (now reverted).
Product "KRCH-FL020"
Product "9420030005904"
This worked and the products synced after the change, but it is unclear why they didn't sync automatically for several days after being "Approved for Shopify".