Electron / React App JavaScript Disabled

I am building a react app packaged with electron builder, and everything works fine in localhost, but when I package the app and its running from the index.html file in the main build folder, index.html’s contents says “You need to enable javascript to run this app.” I have tried a lot of things, and have narrowed the cause of the issue to changing the mainWindow.loadURL() to the index.html file from localhost. We use IPC communication and autoupdate, so I believe we must use nodeIntegration (set to default = true). Please let me know what I am doing wrong, as this contract was due yesterday. I have tried nodeIntegration: true, and nodeIntegration: false, as well as many other things. Again, the issue is ONLY when I set the windows loadURL to the index.html file.