I noticed when I was away at Christmas, that when I wanted to get a file that is stored on my PC, it wasn't available via the Android app on my phone. It did however appear eventually.
I have noticed this again having installed the app on a new Tablet (Again Android). To clarify, I have about 33Gb of my 200Gb currently in use, which consists of lots of stuff between 1kb and no more than a few MB for Camera Stills and Video, so it is a lot to index.. but thus far, according to the app on my new Tablet, there are 2 Main folders shown (There are 10) a few sub-folders, and a grand total of 4 files - 10s of Thousands short.
After 2 days, I would have expected a few more files available, and also it woul dbe nice if it didn't sit there doing nothing at all (With the spinning "busy" icon) for ages, sometimes indefinitely.