cannot email ebooks anymore

I used to be able to email ebooks to my partner but now a get a "failed" error. I have upgraded to El Capitan version 10.11.4 on my mac. i also no longer have the "send to device" icon on my tool bar and have tried multiple times to remove and replace it in preferences but no go. Help! i really miss be able to use Calibre v 2.56.0.

Thank you in advance.

btw, how will i know when someone has responded to :help:my query?

Deb