Ionic2 - HTTP Error 503: POST https://res.ionic.io/api/v1/upload

This is an ionic server side issue (ionic forum)

You can either wait till the service is back online or you can generate the resources locally (from ionic 5). You can do this simply by running the following console commands from your project folder:

Step 1: install cordova-res tool

$ npm install -g cordova-res

Step2: generate the resources

$ cordova-res