(NOTE: this is a duplicate bug report, I made a mistake with the first one.)
Zombies (or other mobs) spawn with a 0% probability to spawn with the CanPickUpLoot activated. When I manually spawn zombies and scatter some items around the place, none of them pick the item up but a large amount of zombies should've picked at least one of the items in past versions. I summoned a zombie with a CanPickUpLoot tag on and they were able to pick the items up without any problems.
Is this a bug or an intended change?
Check your difficulty setting, which has to be set to Hard for zombies to spawn with the ability to pick up loot (which I can confirm still works for natural spawns as well as spawn eggs).