There's bots that search for that port and then use password crackers to get in. I had it set up for a bit on my HTPC but had to shut down that port. Of course I could use a stronger password as the one I had was simple for local network use.
I grabbed it for my phone and kindle fire, and they both work fine. Maybe remove from your device and re-install, Amazon keeps it as an app you purchased so you shouldn't have a problem installing it to your phone again.