I am having a similar issue. I have a new install:
www.ads-software.com 4.1.1.
Private Only Plugin 3.5.1.
Site URL: https://www.ilovelorna.info
No matter what I do I cannot see my logo on the login screen. The URL to the file I believe is correct. The permissions on the file are 777. Whether I set the height value or not no logo displays. Not sure what to do next.
Jay