Your PowerPress settings are stored in your WordPress database. Deleting the plugin files on your WordPress site doesn't change that.
Please follow these steps:
1.) Go to blubrry.com and if you're already logged in, log out (if you're not logged in, go to step 2)
2.) Clear your browser cache
3.) Log into your WordPress dashboard and go to PowerPress >> Settings, Advanced Mode >> Services & Stats and click the "Click here to configure..." button
4.) Enter your Blubrry username and password into the popup box and click Remove and follow any confirmation screens that come up after
5.) Repeat steps 3 and 4 but instead of clicking Remove, click Save instead to reauthorize your site's connection to your Blubrry account