Sounds a lot like a CORS problem. Explanations:
https://blog.nraboy.com/2015/05/whitelist-external-resources-for-use-in-ionic-framework/
Making REST call from Ionic
Make sure you’ve done the following;
In your index.html, have a Content-Security-Policy tag, e.g:
<meta http-equiv="Content-Security-Policy" content="default-src *; script-src 'self' 'unsafe-inline' 'unsafe-eval' *; style-src 'self' 'unsafe-inline' *">
Make sure you’ve installed the Cordova Whitelist plugin, so your package.json should look like:
"cordovaPlugins": [
...
"cordova-plugin-whitelist",
...
And in your config.xml you would have:
<access origin="*"/>
Not sure if ALL of these are necessary, and probably some of the above settings are too “wide” and you can tighten them to improve security. But you can start tweaking that after you’ve got your stuff working.