Variables in rules has stopped working

Why would my variable assignee options not be available in my rules builder? I have a rule where I’m trying to @mention the assignee as well as assign a newly created subtask to the assignee of the parent task.

  1. In the new rules builder, I’m adding a comment to a task where I want to @mention the assignee. When I select the + sign to add variables only Dates and Custom fields options are available, the people option is no longer available.
    add-variable1

  2. In the same rules builder, I’m also adding a subtask that should be assigned to the parent task assignee. When I click the + sign next to the assignee field there are no options available.
    add-variable2