After upgrading its not working!!!

After upgrading WordPress to 3.6 and your Plugin to 3.8.8 I am getting nothing and crippling my business. People are submitting payments but nothing is happening. The page just reloads. Authorize.net gets nothing no emails are sent, nada. My premium features aren’t working either. I paid for all of them and not one is working with recent upgrade. Your Single Page Checkout made a huge mess of my site and I had to remove the file to get my website back up.
It was working perfectly before the last update you put out. I have tried reverting to previous versions but nothing is working now.

I can gladly send login info and url

http://wordpress.org/plugins/wp-invoice/