We are sorry for the trouble. As described te email button is not working.
++ Adding to the discussion
Do you get any error message or code while using the email button? If yes please share the screenshot of the same for better understanding.
Are you on a Mac or Windows machine? and what is the version of the OS? Please try to repair the installation (For Windows Only) Go to Help > Repair Installation and see if that works.
What is the version of the Adobe Acrobat/Reader DC you are using? To check the version go to Help > About Adobe Acrobat/Reader DC and make sure you have the latest version 20.009.20067 installed. Go to Help > Check for Updates.