Error: Failed to instantiate module restangular due to: '_' is undefined
It's a simple oversight. The '_' (underscore) is a JavaScript utility library that Restangular uses and depends on. Include Lodash or Undrescore library before the AngularJS library (in your HTML):
<script src="lodash.js"></script>or
<script src="underscore.js"></script>PS: Double check the library script and path exist as referenced in your SCRIPT tag.
Additional readings: