Think this is the issue:
17/March/2016:
WWO Free API signup has now been suspended. Therefore we will not be issuing any new Free API keys. The existing Free API keys issued will continue to work and no change is required at user end. Also all existing Free API keys will be allowed 1,000 request per day.
For new users to use our Weather API they will be issued Premium Trial key for free testing for 60 days and user may upgrade by purchasing a weather subscription at anytime.
Thank you,
World Weather Online API Team