What do you mean can't activate the button, what do you do and what happens ?
What version of avast are you using, latest is 4.8.1335.
The new submission process doesn't actually get sent by email but you start out by selecting (right click) the file in the chest and choose Email to Alwil Software and you should get a form (similar to the image, slightly older version) and when complete there is a Submit button and not a Send button, so is that what you meant ?