R6900P only a front USB and my flash drive "refreshing" continuous

I am frustrated, all Android devices can't remotely connect, always "refreshing". I saw other topics on this, but not about simply plugging a 30Gb flash drive in the 3.0 port. I can see the drive locally, and remotely using browser interface, but not through the app. I am using the latest firmware.

Also, my router only has one USB port in the front. All images and spec sheets show a front and rear USB port. I was disappointed when I discovered this.