Items Tag does not accept Multiple Sub-tags (Advancements)

When you put multiple sub-tags under the items tag of an advancement JSON file, it won't work. For example, if you put two sub-tags under the items tag, the game doesn't accept it.

What I expect to happen:
The game will accept both of the sub-tags.

What happened:
It didn't.

_{If you didn't understand my explanation, please refer to the attached JSON code.}