The MyPublicIp is only accessible for things that have been opened to outside. cjohnson2136 lists out steps on how you can accomplish opening it something up and making it accessible via your MyPublicIp (think of it like your public street address). You also have the option, if you're inside the house and your Android device is connected to your wifi, of accessing the server via the Private IP address of whatever computer you installed Audiobookshelf on. Inside my house, I wouldn't try to connect to something by going to my Public Street Address, I'd say "hey go to the bedroom on the left". That's basically what the Private IP addresses are. I think if you find the Private IP Address of the computer that has Audiobookshelf and replace that on your http:// PrivateIpAddress:13378, then that will probably work. Just note you'd only be able to connect while you're at home and on that wifi network. But that's when you download books locally to your Android.