Stumbleupon – Error – Bad User/pass

I recieve the following error when trying to submit a test post to Stumbleupon, I’ve tried both email address and username in the username field and retyped the password multiple times but to no effect:

Array ( [pgID] => [isPosted] => 0 [pDate] => 2015-01-20 20:52:39 [Error] => ERROR – BAD USER/PASS )

Any suggestions on how I can resolve this issue?

https://wordpress.org/plugins/social-networks-auto-poster-facebook-twitter-g/