I can login but cannot access dashboard

hi guys,
I can login to my wordpress selfhosted blog, but i cannot access my dashboard. When I clicked login button, it redirect to https://myblog.com/wp-admin/, but the result is not found page/404.

I’m sure that i can login because at meta link sidebar, written: logout. when i clicked the logout link, it came back to https://myblog.com/wp-login.php it written: you’ve successfully logout.