This package was supposed to have been delivered yesterday.
This package was supposed to be delivered yesterday.
Please explain the difference.
And my doubt is generally we use simple past when we say things happened in the past. But why we use present perfect in this situation?
And one more doubt is we use has for singular subjects as "This package has been delivered". But why we use have been with supposed to?
Correct me if I'm wrong and please explain the grammar relevant to this.