In order for the email signature to work in Version 11.0, please do add the signature first and then go to Admin - Notification Rules - Replying to a Request template - Customize template and add the below variable
$EmailSignature.
Go to Home page and in the top right corner click the image of Administrator/support rep . A drop-down will appear and click on personalize where you
need to provider the Signature and save it
Once done, clear the browser cache and see if the signature works.
NOTE:- You need to personalize signature for each support rep separately