Electron needs page reload to show content

I'm new to Electron, my goal is to run a Django app within. The Django app has been compiled using PyInstaller and placed correctly within my electron project structure.

My problem is that when I start electron (electron .) its blank window opens. I need to hit refresh to show to right content. I cannot get this to work such that the page is reloaded to show content during electron opening. I tried the reload() and reloadIgnoringCache() option but it doesn't help...

Analysing my window webContents parameters I can see that my window initially gets currentIndex: -1 and after manually reloading currentIndex: 0 (not sure if that is relevant...).

Here is the relevant part of my main.js file:

app.on('ready', function() {
log.info('App is ready?!....');

var openWindow = function(mainAddr){
    mainWindow = new BrowserWindow({width: 1200, height: 800, backgroundColor: '#eeeeee', show:false});
    mainWindow.loadURL(mainAddr);
    mainWindow.webContents.on('did-finish-load', function() {
        mainWindow.show();

    });
    mainWindow.webContents.session.clearCache(function() {
        console.log("Cache has been cleared.");
    });
    mainWindow.webContents.reloadIgnoringCache();
    mainWindow.webContents.openDevTools();
    mainWindow.on('closed', function() {
        mainWindow = null;
        subpy.kill('SIGINT');
    });


};

via user1544500