This is how it is supposed to be. Octopi are a summon, similar to Frostprey, Phoenix, Bahamut, etc. Pets do not loot items from Monsters killed by Summons. This was changed in an update, I think at least a year ago by now. It is supposed to deter macro botting to farm in maps like voodoos for stoppers.
https://royals.ms/forum/threads/update-58-13-12-2018.132322/ Misc: Items dropped by mobs that are killed by summons will no longer be lootable by pets. NOTE: This change has been made to reduce the effectiveness of summon botting.