Fix that worked for me since my Protocol handlers was empty
https://productforums.google.com/forum/#!topic/gmail/CQMCGRvyhCM
See redfish43 reply , to sum up
For mailto: - Make sure you are logged in to Gmail and the active window is your main Gmail page (or nothing will happen). - Copy/paste this into the address bar:
javascript:navigator.registerProtocolHandler("mailto","https://mail.google.com/mail/?extsrc=mailto&url=%s","Gmail")
Add the javascript: to the front again if needed, because when you pasted it, Chrome probably trimmed everything before and including the colon. Then hit enter.
When popup window opens click on "Allow"