Apple Mail, window doesn't open when opening mail.

This isn't a big deal, but when I would open Apples Mail app' the viewer window would open with it, after the upgrade it doesn't. It counts the e-mail I have but the window doesn't pop open, all other apps windows open when selected.

Any advice? Like I said its no big deal, I'd just like it to work properly.

Thanks.

Mail: Version 13.0 (3601.0.10)

OS: 10.15.1