Perhaps someone has already pointed this out, but in case not...
The way I got the Google shorter to start working again, was to generate my own API key (you'll need to do that in your Google Developer account — set one up if you need to) and add it to the scripting in this Workflow, as follows:
Change this:
0 : {'api_url':'https://www.googleapis.com/urlshortener/v1/url','title':'goo.gl','des':'http://goo.gl/'},
to this:
0 : {'api_url':'https://www.googleapis.com/urlshortener/v1/url?key=YOUR-API-KEY','title':'goo.gl','des':'http://goo.gl/'},
It now works just fine.
I also added my own API key to the bit.y and j.mp shorteners. Apparently the API used (by the kind developer of this workflow) was reaching its limit. Now those two services also work again.