Unless you are hosting the UI files on the Raspberry Pi as well, Apache is not used. Also, I don’t see any errors in the log output you pasted. This is also why /var/www is empty. The firmware actually launches it’s own web server for the data and uses the Internet for the UI files. Therefore, if you don’t have a working Internet connection, this could be the cause of the blank page.
Can you try an application or browser extension? We have extensions for Chrome and Firefox and apps for OS X, iOS, Android, Blackberry 10, Windows Phone 8 and Amazon Fire. The apps do NOT need an Internet connection and have all the UI assets they need bundled inside.
Also, if you are interested in copying the UI files to the Raspberry Pi and using Apache to host them we have a guide for this: https://opensprinkler.freshdesk.com/support/solutions/articles/5000164006-using-a-different-server-for-ui-assets. In the future, we will consider preconfiguring the SD card for the OSPi to automatically do this however the reason we don’t the UI would no longer get updated automatically, like it does when hosted on the Internet.
Also, none of this helps, can you open the Developer Tools (in Chrome right click and push “Inspect Element”) and navigate to the “Console” tab? Here you will see any errors listed in red. If there are any, can you please share them.