I spent a great deal of time investigating this one and thought I would share what I found, including the eventual solution.
Extensive googling leads to the repeated suggestion of adding:
this.setIntegerProperty("loadUrlTimeoutValue", 60000);
I found that the 'proper' place for this code was in a java file (in my case called MainActivity.java) located in c:[...]\platforms\android\src\com\ionicframework\client2583743
However, after doing so, my build failed with a "cannot find symbol" exception indicating the problem was with the code I added, though java could find the method:
symbol: method setIntegerProperty(String,int)
There is, however, another way of adding this value, according to SO: https://stackoverflow.com/a/22620404/1308787
I opened config.xml outside of VS in a text editor and added this line:
<preference name="loadUrlTimeoutValue" value="60000" />
Additionally, the following fix works:
https://www.robertkehoe.com/2013/01/fix-for-phonegap-connection-to-server-was-unsuccessful/
Basically this fix requires the replacement of index.html with a window.location redirect to the actual page.
However I found that VS2015 cannot attach a debugger when using this technique. I get a "Unable to attach. The operation was cancelled" in VS, but the emulator continues to work, without the Application error above, but also without a debugger attached.