The option to create a "Subtask" has disappeared from all the issues (Story, Bug, Task).

"Subtask" was automatically configured as an issue type when I created the board and it still exists when I check the project settings > issue types.

I can also still "Group By Subtasks" on my Next-Gen board.

What am I missing? How do I create and see subtasks? And I'm not referring to "Child Issues".
Thank you.