I just installed civi 4.7.27 on Wordpress 4.9.1 into a subdomain example.mysite.com The civimail New Mailing page is blank and the System Status page is blank. Other pages are probably blank too.
I want to let everyone know that I have resolved this issue. Apparently when installing Civi into a subdomain, you need to configure the resource urls to absolute paths instead of relying on the short codes. See screenshot below. If you ever have this issue, try making your resource urls look like that.
Please double/triple check that the paths you have set for Directories and Resources (both under Admin > System Settings) are correct.