Are you passing the notification text in your tests? Just checking
because it wasn't in your sample when you constructed the URL manually.
In ruby, would be something like this:
require 'digest/md5'
digest = Digest::MD5.hexdigest('add...@gmail.com')
Net::HTTP.post_form(URI.parse('http://api.notify.io/v1/notify/'+digest),
{'api_key' => 'source-api-key', 'text' => 'Hi there'})
Working just fine for me.
David