I had a Surface RT with Windows RT 8.1 and have recently switched to an ASUS Transformer Book T100 with Windows 8.1, and on both systems I had the Windows Store apps all up-to-date. Something in the (HTML?) formatting of the Windows Server 2012 R2 Essentials health report is causing it not to display properly in the Mail app on Win8.1. I basically just get a couple headings with a ton of white space and no real body text or images. There is no download option to download the content of the message either.
I also have a Nokia Lumia 920 and the reports display just fine on it.
Why isn't this working?
I didn't check the version of the mail app on the Surface, but on the T100, it's 17.4.9600.16384.
Just FYI: I love the "My Server" app, but I do have a few qualms about the Windows Store Remote Desktop app.