With the new user interface release by MetaMask, we noticed that the service is no longer fully compatible with Bancor conversions.
As this is a breaking change for Bancor users, we currently recommend downgrading back to the old user interface in order to execute conversions as you did before. We are working on a fix to ensure that Bancor conversions are compatible with the new MetaMask interface.
In the meantime, here are the steps needed to perform the downgrade:
click on the wallet icon on the top right corner. this will open the account settings menu.
click on the "settings" icon on the bottom of this menu. this will lead you to the settings section of the wallet
scroll down to the bottom of this page to find the "use old UI" button.
click the "use old UI" button
now you will be using the old user interface and will be able to execute conversions as before.