SSO between Envato and Codecanyon on Checkout

I have been struggling with this process for a very long time. Even if I login to account.envato switch to envato market place and select plugins, find the plugin and add to cart, all while already logged into envato, I am always forced to reset my password. I cannot not purchase a codecanyon plugin with envato account, why haven’t you guys fixed this, it is a very very old problem.